FDA WARNS AGAINST SOLE USE OF LONG-ACTING BETA AGONISTS IN ASTHMA

 

 

 

FDA Warns Against Sole Use of Long-Acting Beta Agonists in Asthma

from Medscape

Long-acting beta agonists should not be used alone in asthma, the FDA warns. The drugs at issue include the single-agent LABAs Serevent and Foradil.

Because LABAs have been associated with severe worsening of symptoms, the agency is requiring that labels carry the following guidance:

• LABAs are contraindicated without the use of a controller medication, such as an inhaled corticosteroid.
• Long-term use is only indicated for patients whose disease doesn’t respond to controller medications.
• LABAs should be used for the shortest period possible.
• To ensure compliance, children and adolescents should only use LABAs that contain an inhaled corticosteroid.

The recommendations do not apply to use of LABAs in chronic obstructive pulmonary disease.

LINK:

FDA Announces New Safety Controls for LABAS

AAAAI: What do you do now? Use of LABAS in light of the recent FDA decision

Contact Dermatitis

from Healthline.com
Definition:

Contact dermatitis is an inflammation of the skin caused by direct contact with an irritating substance.
Alternative Names

Dermatitis – contact; Allergic dermatitis; Dermatitis – allergic; Poison ivy; Poison oak; Poison sumac
Causes, incidence, and risk factors

Contact dermatitis is an inflammation of the skin caused by direct contact with an irritating or allergy-causing substance (irritant or allergen). Reactions may vary in the same person over time. A history of any type of allergies increases the risk for this condition.

Irritant dermatitis, the most common type of contact dermatitis, involves inflammation resulting from contact with acids, alkaline materials such assoaps and detergents, solvents, or other chemicals. The reaction usually resembles a burn.

Allergic contact dermatitis, the second most common type of contact dermatitis, is caused by exposure to a substance or material to which you have become extra sensitive or allergic. The allergic reaction is often delayed, with the rash appearing 24 – 48 hours after exposure. The skin inflammation varies from mild irritation and redness to open sores, depending on the type of irritant, the body part affected, and your sensitivity.

Overtreatment dermatitis is a form of contact dermatitis that occurs when treatment for another skin disorder causes irritation.

Common allergens associated with contact dermatitis include:

* Poison ivy, poison oak, poison sumac
* Other plants
* Nickel or other metals
* Medications
o Antibiotics, especially those applied to the surface of the skin (topical)
o Topical anesthetics
o Other medications
* Rubber or latex
* Cosmetics
* Fabrics and clothing
* Detergents
* Solvents
* Adhesives
* Fragrances, perfumes
* Other chemicals and substances

Contact dermatitis may involve a reaction to a substance that you are exposed to, or use repeatedly. Although there may be no initial reaction, regular use (for example,nail polish remover, preservatives in contact lens solutions, or repeated contact with metals in earring posts and the metal backs of watches) can eventually cause cause sensitivity and reaction to the product.

Some products cause a reaction only when they contact the skin and are exposed to sunlight (photosensitivity). These include shaving lotions, sunscreens, sulfa ointments, some perfumes, coal tar products, and oil from the skin of a lime. A few airborne allergens, such as ragweed or insecticide spray, can cause contact dermatitis.

Symptoms

* Itching (pruritus) of the skin in exposed areas
* Skin redness or inflammation in the exposed area
* Tenderness of the skin in the exposed area
* Localized swelling of the skin
* Warmth of the exposed area (may occur)
* Skin lesion or rash at the site of exposure
o Lesions of any type: redness, rash, papules (pimple-like), vesicles, and bullae (blisters)
o May involve oozing, draining, or crusting
o May become scaly, raw, or thickened

Signs and tests

The diagnosis is primarily based on the skin appearance and a history of exposure to an irritant or an allergen.

According to the American Academy of Allergy, Asthma, and Immunology, “patch testing is the gold standard for contact allergen identification.” Allergy testing with skin patches may isolate the suspected allergen that is causing the reaction.

Patch testing is used for patients who have chronic, recurring contact dermatitis. It requires three office visits and must be done by a clinician with detailed experience in the procedures and interpretation of results. On the first visit, small patches of potential allergens are applied to the skin. These patches are removed 48 hours later to see if a reaction has occurred. A third visit approximately 2 days later is to evaluate for any delayed reaction. You should bring suspected materials with you, especially if you have already tested those materials on a small area of your skin and noticed a reaction.

Other tests may be used to rule out other possible causes, including skin lesion biopsy or culture of the skin lesion (see skin or mucosal biopsy culture).

How can I help my doctor diagnose my skin condition?

Keep a “diary” of when your symptoms appear, get worse or improve. It also helps to write down where your symptoms occur on your body, and how long they last. If you notice that your skin gets worse after certain activities, record the reaction and the activity in as much detail as possible.

Workers in some occupations are more likely to develop allergic contact dermatitis, so it’s important to describe your work to your doctor. If you handle chemicals during the day, make a list of these or find their Material Safety Data Sheets (MSDS).

Treatment

Successful treatment of dermatitis symptoms depends on getting an accurate diagnosis from your physician. Depending on the type of dermatitis and the severity of skin reactions, a physician may prescribe corticosteroids, antifungal agents, antihistamines, barrier creams, and moisturizers for your skin, shampoos with salicylic acid, selenium, zinc, or coal tar, and oral medications. These treatments are intended to treat your symptoms and improve your skin’s condition.

Because there is often no cure for dermatitis, your physician should discuss ways to avoid allergen and/or irritant contact, and how to take better care of your skin. In addition, reducing stress can improve your immune system response and help restore your skin’s normal integrity

Initial treatment includes thorough washing with lots of water to remove any trace of the irritant that may remain on the skin. You should avoid further exposure to known irritants or allergens.

In some cases, the best treatment is to do nothing to the area.

Corticosteroid skin creams or ointments may reduce inflammation. Carefully follow the instructions when using these creams, because overuse, even of low-strength over-the-counter products, may cause a troublesome skin condition. In severe cases,systemic corticosteroids may be needed to reduce inflammation. These are usually tapered gradually over about 12 days to prevent recurrence of the rash.

Contact dermatitis usually clears up without complications within 2 or 3 weeks, but may return if the substance or material that caused it cannot be identified or avoided. A change of occupation or occupational habits may be necessary if the disorder is caused by occupational exposure.
Complications

Secondary bacterial skin infections may occur.

Call your health care provider if symptoms indicate contact dermatitis and it is severe or there is no improvement after treatment.
Prevention

Avoid contact with known allergens. Use protective gloves or other barriers if contact with substances is likely or unavoidable. Wash skin surfaces thoroughly after contact with substances. Avoid overtreating skin disorders.
References

Gober MD, DeCapite TJ, Gaspari AA. Contact dermatitis. In: Adkinson NF Jr, ed. Middleton’s Allergy: Principles and Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2008:chap 63.

Habif TP. Contact dermatitis and patch testing. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 4.

Lancet Retracts Study Linking Autism to MMR Vaccine

from Medscape
Daniel J. DeNoon

Perspective by Dr. Dennis Niewoehner February 2, 2010 — The venerable British medical journal The Lancet has retracted a 1998 study suggesting a link between autism and childhood vaccination with the measles-mumps-rubella MMR vaccine.

The Lancet tells WebMD that it has retracted “10 or 15″ studies in its 186-year history. The retraction follows the finding of the U.K. General Medical Council (GMC) that says study leader Andrew Wakefield, MD, and two colleagues acted “dishonestly” and “irresponsibly” in conducing their research.

The Lancet specifically refers to claims made in the paper that the 12 children in the study were consecutive patients that appeared for treatment, when the GMC found that several had been selected especially for the study. The paper also claimed that the study was approved by the appropriate ethics committee, when the GMC found it had not been.

“We fully retract this paper from the published record,” The Lancet editors say in a news release.

The retraction means the study will no longer be considered an official part of the scientific literature.

BMJ, formerly known as the British Medical Journal, has competed with The Lancet since 1840. BMJ editor Fiona Godlee says she welcomes the Lancet retraction.

“This will help to restore faith in this globally important vaccine and in the integrity of the scientific literature,” Godlee says in a news release.

In 2004, 10 of Wakefield’s 13 co-authors disavowed the findings of the 1998 study. Although the study never claimed to have definitively proven a link between the MMR vaccine and autism, sensational media reports ignited a public panic. MMR vaccinations fell dramatically.

More rigorous studies have found no link between autism and the MMR vaccine. Last year, the U.S. “vaccine court” rejected U.S. lawsuits claiming that there was a plausible link between the vaccine and autism.

Wakefield continues to proclaim his innocence and defends his earlier work. He now resides in Texas, where he is executive director of an alternative medicine center for autism treatment and research.

SOURCES:

The Lancet, published online Feb. 2, 2010.

SWINE FLU AND YOU

Questions & Answers: Swine Influenza Info from the Centers for Disease Control

What is swine flu?
Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza viruses that causes regular outbreaks in pigs. People do not normally get swine flu, but human infections can and do happen. Swine flu viruses have been reported to spread from person-to-person, but in the past, this transmission was limited and not sustained beyond three people.
How serious is swine flu infection?
Like seasonal flu, swine flu in humans can vary in severity from mild to severe. Between 2005 until January 2009, 12 human cases of swine flu were detected in the U.S. with no deaths occurring. However, swine flu infection can be serious. In September 1988, a previously healthy 32-year-old pregnant woman in Wisconsin was hospitalized for pneumonia after being infected with swine flu and died 8 days later. A swine flu outbreak in Fort Dix, New Jersey occurred in 1976 that caused more than 200 cases with serious illness in several people and one death.

Can I get swine influenza from eating or preparing pork?
No. Swine influenza viruses are not spread by food. You cannot get swine influenza from eating pork or pork products. Eating properly handled and cooked pork products is safe.

Is this swine flu virus contagious?
CDC has determined that this swine influenza A (H1N1) virus is contagious and is spreading from human to human. However, at this time, it not known how easily the virus spreads between people.

What are the signs and symptoms of swine flu in people?
The symptoms of swine flu in people are similar to the symptoms of regular human flu and include fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting associated with swine flu. In the past, severe illness (pneumonia and respiratory failure) and deaths have been reported with swine flu infection in people. Like seasonal flu, swine flu may cause a worsening of underlying chronic medical conditions.

How does swine flu spread?
Spread of this swine influenza A (H1N1) virus is thought to be happening in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose.

How can someone with the flu infect someone else?
Infected people may be able to infect others beginning 1 day before symptoms develop and up to 7 or more days after becoming sick. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick.

What should I do to keep from getting the flu?
First and most important: wash your hands. Try to stay in good general health. Get plenty of sleep, be physically active, manage your stress, drink plenty of fluids, and eat nutritious food. Try not touch surfaces that may be contaminated with the flu virus. Avoid close contact with people who are sick.

Are there medicines to treat swine flu?
Yes. CDC recommends the use of oseltamivir or zanamivir for the treatment and/or prevention of infection with these swine influenza viruses. Antiviral drugs are prescription medicines (pills, liquid or an inhaler) that fight against the flu by keeping flu viruses from reproducing in your body. If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious flu complications. For treatment, antiviral drugs work best if started soon after getting sick (within 2 days of symptoms).

How long can an infected person spread swine flu to others?
People with swine influenza virus infection should be considered potentially contagious as long as they are symptomatic and possible for up to 7 days following illness onset. Children, especially younger children, might potentially be contagious for longer periods.

What surfaces are most likely to be sources of contamination?
Germs can be spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth. Droplets from a cough or sneeze of an infected person move through the air. Germs can be spread when a person touches respiratory droplets from another person on a surface like a desk and then touches their own eyes, mouth or nose before washing their hands.

How long can viruses live outside the body?
We know that some viruses and bacteria can live 2 hours or longer on surfaces like cafeteria tables, doorknobs, and desks. Frequent handwashing will help you reduce the chance of getting contamination from these common surfaces.

What is the best way to keep from spreading the virus through coughing or sneezing?
If you are sick, limit your contact with other people as much as possible. Do not go to work or school if ill. Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick. Put your used tissue in the waste basket. Cover your cough or sneeze if you do not have a tissue. Then, clean your hands, and do so every time you cough or sneeze.

What is the best technique for washing my hands to avoid getting the flu?
Washing your hands often will help protect you from germs. Wash with soap and water. or clean with alcohol-based hand cleaner. we recommend that when you wash your hands — with soap and warm water — that you wash for 15 to 20 seconds. When soap and water are not available, alcohol-based disposable hand wipes or gel sanitizers may be used. You can find them in most supermarkets and drugstores. If using gel, rub your hands until the gel is dry. The gel doesn’t need water to work; the alcohol in it kills the germs on your hands.

What should I do if I get sick?
If you live in areas where swine influenza cases have been identified and become ill with influenza-like symptoms, including fever, body aches, runny nose, sore throat, nausea, or vomiting or diarrhea, you may want to contact their health care provider, particularly if you are worried about your symptoms. Your health care provider will determine whether influenza testing or treatment is needed.

If you are sick, you should stay home and avoid contact with other people as much as possible to keep from spreading your illness to others. If you become ill and experience any of the following warning signs, seek emergency medical care.

In children emergency warning signs that need urgent medical attention include:

* Fast breathing or trouble breathing
* Bluish skin color
* Not drinking enough fluids
* Not waking up or not interacting
* Being so irritable that the child does not want to be held
* Flu-like symptoms improve but then return with fever and worse cough
* Fever with a rash

In adults, emergency warning signs that need urgent medical attention include:
* Sudden dizziness
* Confusion
* Severe or persistent vomiting
* Pain or pressure in the chest or abdomen
* Difficulty breathing or shortness of breath

Time for Spring Allergies

Pollen Grains

From the AAAI Rhinitis Tips:
Do you have bouts of sneezing and itching, or a runny or stuffy nose that do not seem to go away? If so, you may have rhinitis.

Rhinitis is one of the most common illnesses in the United States , affecting more than 50 million people. It often coexists with other respiratory disorders, such as asthma. Rhinitis has a significant impact on the quality of life of those who suffer from it. In addition, it can contribute to other conditions such as sinus problems, ear problems, sleep problems, and learning problems. In patients with asthma, uncontrolled rhinitis seems to make asthma worse.

Allergic rhinitis
Allergic rhinitis is caused by substances that we breathe called allergens. Allergens are usually harmless substances that can cause problems only in some people. These problems are caused because the immune system of people with allergic rhinitis mistakenly identifies these substances as intruders and generates a reaction against them. During this reaction, the immune system cells release substances such as histamine and leukotrienes that cause the symptoms of allergic rhinitis; these and other substances also cause inflammation in the nasal lining that makes the nose very sensitive to irritants such as smoke and strong odors or to changes in the temperature and humidity of the air.

Causes:

1. When allergic rhinitis is caused by common outdoor allergens, such as airborne tree, grass and weed pollens or mold, it is called seasonal allergic rhinitis, or “hay fever.”
2. Allergic rhinitis is also triggered by common indoor allergens, such as animal dander (dried skin flakes and saliva), indoor mold, droppings from dust mites and cockroach particles. This is called perennial allergic rhinitis.

Symptoms

Sneezing
Stuffy nose (congestion)
Runny nose
Itching in the nose, roof of the mouth, throat, eyes and ears
Diagnosis
If you have symptoms of allergic rhinitis, an allergist/immunologist can help determine which specific allergens are triggering your illness. He or she will take a thorough health history, and then test use to determine if you have allergies. Skin tests or blood tests are the most common methods for determining your allergic rhinitis triggers.

What to Do During Pollen Season:
When outdoor pollens are high, remain indoors, particularly in the late morning. Pollen grains can cause significant allergic symptoms like asthma and allergic rhinitis, particularly during the spring and the fall. It is difficult to avoid pollen because it is windborne and can cover wide distances. Short of moving to a different location, here are some tips for avoiding pollen during the season.

1. The pollen count is usually highest in the late morning and early afternoon particularly during sunny, windy days. The pollen count measures the concentration of a specific pollen like birch tree pollen, in the area in a specific area and time. A pollen count is a useful guide for when it is advisable to stay indoors and avoid contact with pollen.
2. Keep the windows and doors closed during the allergy season.
3. Install a room air conditioner with a special filter.The special filter (High Efficiency Particulate Air or HEPA filter) traps airborne allergens. If the house does not have central air, the best spot to put the air conditioner and filter would be the bedroom. Change the filters frequently. An allergic person should also use the car air conditioner to decrease pollen exposure when commuting. Pollen allergic persons should not have a window fan blowing into their bedroom as this will maintain outdoor pollen exposure all night.
4. Avoid working outdoors, if you must wear a special face mask. The face mask is designed to filter pollen out of the air and keep it from reaching the nasal passages.
5. Consider taking a vacation at the height of the pollen season. Preferably at a location where the pollen exposure is minimal, like the seashore.

Links: Allergy Medications
Info on Allergy Shots

No Evidence Supports Link Between Vaccines and Autism

No Evidence Supports Previously Held Link Between Vaccines and Autism

Laurie Barclay, MD
from Medscape
February 9, 2009 — There is no cause for parental concern that childhood immunization might cause autism, according to the results of a new review that shows no link between vaccines and autism. The review is published in the February 15 issue of Clinical Infectious Diseases.

“Vaccines don’t cause autism — 20 studies now show no link between vaccines and autism,” senior author Paul A. Offit, MD, chief of infectious diseases, The Children’s Hospital of Philadelphia in Pennsylvania, told Medscape Infectious Diseases. “I think that many people are reassured by these studies, although there are still a group of parents who hold that vaccines cause autism, much as some people hold a religious belief. To those people, it really doesn’t matter how many studies you do, it’s not going to change their minds.”

More education is needed to prevent further disease resurgence among children whose parents have refused vaccination based on this unfounded fear, he added.

Three Theoretical Links

Three specific hypotheses have been offered to suggest a theoretical link between vaccines and autism. The review describes how each of these theories originated and summarizes the pertinent epidemiological data, which refute the 3 hypotheses.

“The first theory concerned the Measles-Mumps-Rubella (MMR) vaccine; the second, that it wasn’t the MMR vaccine specifically but a mercury-containing preservative, thimerosal; and the third, that the simultaneous administration of many vaccines is just too much for a young child’s immune system,” Bryan H. King, MD, co-chair, American Academy of Child and Adolescent Psychiatry Autism and Intellectual Disabilities Committee, told Medscape Infectious Diseases when asked for independent comment.

The first hypothesis is that the combination MMR vaccine damages the gastrointestinal lining, thereby permitting the entrance of encephalopathic proteins and causing autism. After publication of a 1998 study in The Lancet suggesting an association between MMR vaccine and autism, 13 subsequent studies performed in 5 different countries showed no such link. The reviewers concluded that no data supported any causal connection between the MMR vaccine and autism, and that any apparent association was coincidental, because the MMR vaccine is typically administered at the age when symptoms of autism first emerge.

“While rates of immunization have been constant or declined, the incidence of autism has increased, and the rate of autism in vaccinated and unvaccinated children is the same,” said Dr. King, who is professor and vice chair of Psychiatry and Behavioral Sciences and director of Child and Adolescent Psychiatry at University of Washington and Seattle Children’s Hospital. “Neither the timing of onset, nor the severity of autism, differ whether or when a child gets immunized,”

The second hypothesis is that thimerosal, an ethyl mercury–containing preservative used for more than 50 years in some vaccines, causes central nervous system toxicity. However, the review describes 7 studies from 5 countries demonstrating that autism rates were not affected by the presence or absence of thimerosal in vaccines.

These 20 epidemiologic studies showing that neither thimerosal nor MMR vaccine causes autism were conducted by many different investigators, using a variety of epidemiologic and statistical methods.

“Even very rare associations, if they existed, would have been detectable given the large size of studied populations,” Dr. King said. “Studies on the causes of autism should focus on more promising leads.”

The third hypothesis is that giving multiple vaccines simultaneously overwhelms or weakens the immune system. In rebuttal, the review authors point out that the immune system in childhood routinely processes far more antigenic material than the relatively small amount contained in vaccines, and that it is biologically implausible that vaccines overwhelm a child’s immune system, even if the system is still immature.

“The challenge to the immune system from modern vaccines — even in multiple combinations — is actually significantly less than was given routinely to children back in 1980 (long before the autism epidemic),” Dr. King said.

Finally, the review authors note that autism is not triggered by an immune response, and they suggest that future research on the biological basis of autism should prove or refute alternative, more plausible hypotheses.

While the risks of vaccination concerning autism are theoretical and shown not to be valid, the risks of not being vaccinated are real and sometimes fatal.

“We’ve already seen the outcomes of choosing not to comply — over the last 10 years or so, we’ve had outbreaks of pertussis among a relatively unvaccinated population of children,” Dr. Offit said. “We had a measles outbreak in this country that was bigger than anything we’ve had in a decade. Now we have a cluster of cases of Haemophilus Influenzae meningitis where 3 parents chose not to have their child vaccinated; all 3 children got meningitis, and all 3 of them died.”

Dr. Offit noted, “The question becomes, ultimately, when do we reach the tipping point? When do we say that exempting from vaccines is creating a problem not only for those children whose parents choose not to vaccinate but for those children in the community?”

Education of the lay public, as well as the healthcare community, is needed if unfounded fears of vaccination are to be dispelled.

The “Right to Catch and Transmit Potentially Fatal Infection”

“Public health officials and the academic community are really trying to communicate this science to the public, but it’s a real challenge,” Dr. Offit said. “Is it your right to catch and transmit a potentially fatal infection? Right now, the answer to that question is yes, but we’ll see how long it takes before the answer to that question is no.”

He added that it would be unethical to do a prospective study in which some children were not vaccinated, given the known harms of failure to vaccinate, and that retrospective studies would have methodological issues because the groups would differ in characteristics other than their vaccination status.

“Focusing our precious research time and talent on questions that have been asked and answered not only contributes to ongoing confusion — for example, about whether or not to be immunized — but also will delay us from finding real answers to this critical problem,” Dr. King concluded. “Parents and clinicians should have candid discussions about the risks and benefits of vaccination including the avoidance of potentially catastrophic diseases. It will be hard not to mention autism in this context, as it may give the impression that doctors are trying to hide something, and parents should feel empowered to ask these and any other questions of their clinicians, but on the other hand, constantly linking autism and vaccines in the same sentence may continue to suggest that a relationship exists when there is no evidence to support it.”

Telling Food Allergies From False Alarms

from The New York Times
By TARA PARKER-POPE
Published: February 2, 2009
For Ingelisa Keeling, a Houston mother of three children with multiple allergies, mealtime was a struggle. Nuts, eggs, wheat, beef, peas and rice were all off limits — banned by the children’s allergist.

But recently, Mrs. Keeling learned that her family’s diet need not be so restrictive. Although her children do have real allergies — to peanuts, milk and eggs, among other foods — extensive testing at a major allergy center showed that they were not in fact allergic to many of the foods they had been avoiding. Her 2-year-old son, who had been living on a diet primarily of potatoes, fruit and hypoallergenic formula, has resumed eating wheat, bananas, beef, peas, rice and corn.

“His diet had become so, so restricted that nutrition had become a real concern,” said Mrs. Keeling, who traveled to specialists at National Jewish Health in Denver last summer for answers about her children’s diet and eczema problems. Among other findings, she learned that neither of her younger children was really allergic to wheat.

“That’s the big one,” she said. “Wheat is in everything, so it makes life a whole lot easier.”

Doctors say that misdiagnosed food allergies appear to be on the rise, and countless families are needlessly avoiding certain foods and spending hundreds of dollars on costly nonallergenic supplements. In extreme cases, misdiagnosed allergies have put children at risk for malnutrition.

And avoiding food in the mistaken fear of allergy may be making the overall problem worse — by making children more sensitive to certain foods when they finally do eat them.

More than 11 million Americans, including 3 million children, are estimated to have food allergies, most commonly to milk, eggs, peanuts and soy. The prevalence among children has risen 18 percent in the past decade, according to the Centers for Disease Control and Prevention. While the increase appears to be real, so does the increase in misdiagnosis.

The culprit appears to be the widespread use of simple blood tests for antibodies that could signal a reaction to food. The tests have emerged as a quick, convenient alternative to uncomfortable skin testing and time-consuming “food challenge” tests, which measure a child’s reaction to eating certain foods under a doctor’s supervision.

While the blood tests can help doctors identify potentially risky foods, they aren’t always reliable. A 2007 issue of The Annals of Asthma, Allergy & Immunology reported on research at Johns Hopkins Children’s Center, finding that blood allergy tests could both under- and overestimate the body’s immune response. A 2003 report in Pediatrics said a positive result on a blood allergy test correlated with a real-world food allergy in fewer than half the cases.

“The only true test of whether you’re allergic to a food or not is whether you can eat it and not react to it,” said Dr. David Fleischer, an assistant professor of pediatrics at National Jewish Health. In one recent case there, doctors treated a young boy who had been given a feeding tube because blood tests indicated he was allergic to virtually every food. Food challenge testing allowed doctors to quickly reintroduce 20 foods into his diet, and they expect more to be added.

Blood tests may be unreliable because they fail to distinguish between similar proteins in different foods. A child who is allergic to peanuts, for instance, might test positive for allergies to soy, green beans, peas and kidney beans. Children with milk allergies may test positive for beef allergy.

The most important question in diagnosing food allergy is whether the child has tolerated the food in the past, Dr. Fleischer says. While some severe allergies are obvious, parents given a positive blood test result should seek advice from an experienced allergist who performs medically supervised food challenge testing.

Even when a food allergy has been confirmed, parents should have children retested, because many allergies are outgrown, particularly in the cases of milk, eggs, soy and wheat.

Doctors’ groups are also starting to acknowledge that some of their own policies may have contributed to overtesting and misdiagnoses. A committee for the American Academy of Asthma Allergy and Immunology is considering revised guidelines recommending earlier introduction of foods like eggs, peanuts and shellfish, which in the past have been delayed until age 2 or 3. A 2008 study of 10,000 British children, reported in The Journal of Allergy and Clinical Immunology, found that early exposure to peanuts lowered allergy risk.

Just as an allergy indicates oversensitivity to certain foods, it may be that doctors and parents have become oversensitive to food allergies. In an essay in The British Medical Journal in December, Dr. Nicholas A. Christakis, a professor at Harvard Medical School, argues that an “overreaction” to allergy is leading to unnecessary testing and false positives.

“If the kid has been doing fine, I would advise parents not to get allergy testing, because the results are more likely to be false positives than true positives,” Dr. Christakis said in an interview. “If they do think they need allergy testing, be extremely measured and go to reputable people.”