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Friday, May 25, 2012

Post #30 Food Allergies: What and What Not To Do

I recently reread an article that I thought poignantly summarized how food allergies should be approached by a clinician. Although the article was written in 2010, the information is scientifically sound and current. I bolded the recommendations as written by the author and added some commentary where appropriate. Parents can use this information to assess whether their doctor is appropriately advising them on how to approach the work-up of their child's food allergies (or lack thereof).

From Medscape Allergy & Immunology, Food Allergy: What You Need to Know by Stephanie A. Leonard, MD, Posted: 11/15/2010.

1. Delaying of potentially allergenic foods until 1, 2, or 3 years of age has not been shown to prevent food allergies. In 2008, the American Academy of Pediatrics amended their earlier position and no longer recommends avoidance of such foods as a preventive measure.

There was an excellent study done in the Journal of Clinical Immunology in 2008 showing that early consumption of peanuts in infancy is associated with a lower prevalence of peanut allergy. Essentially, the study looked at the prevalence of peanut allergies in Jewish children in the UK (where peanuts are avoided in infancy) vs Jewish children in Israel (where peanuts are fed in infancy). The UK had a 10 fold higher prevalence in peanut allergies.

2. Food allergic patients, especially those with a new diagnosis, should be seen by an allergist for complete work-up, education, and management. Children can outgrow their food allergies, and yearly monitoring is warranted.

A complete work-up should include a thorough history and possibly skin testing and/or blood work. The skin tests and blood work are NOT highly accurate when used as a stand-alone test. They must be analyzed in conjunction with a good history and exam to achieve the most accurate diagnosis. Testing by itself will lead to 50% false positives.

3. Specific food IgE levels can be measured after careful history-taking identifies potential allergens. The focus should be on foods ingested within 2 hours leading up to an acute reaction or foods that appear to consistently exacerbate eczema.

IgE levels are the most common blood tests done to help identify food allergies. Common names for the IgE blood test are the RAST (RadioAllergoSorbent Test) or the ImmunoCAP test.

4. Specific food IgE testing panels are not recommended because of the occurrence of false positives and the potential for foods that an individual has been tolerating to be unnecessarily removed from their diet.

Removing healthy foods that a child has been tolerating well, simply because a test shows a possible allergy can make a family's life unnecessarily difficult and possibly hurt the overall nutritional value of a child's diet. Again, a thorough history and exam with the guidance of an experienced allergist should help prevent unnecessary diet modifications.

5. Removing a previously tolerated food from a patient's diet solely on the basis of an elevated specific IgE can put the patient at risk for developing an actual clinical allergy to that food.

Not only could you make your life more difficult than necessary, you may actually create a true food allergy when there was not one to begin with.

6. An undetectable specific food IgE level is not a guarantee that an individual is not allergic. If the history is suggestive, skin testing should be performed (and possibly an oral food challenge as well) before the food is ingested again.

In addition to false positives, the blood tests may also show FALSE NEGATIVES - meaning even though the blood test was negative, a true food allergy may exist. Again, a thorough history and exam with an allergist is important.

7. Specific food IgE levels help to predict the likelihood of reactivity but not the type or severity of reaction. The significance of the levels varies among foods, so they are not comparable.

The level of IgE is often misinterpreted as the higher it is, the more allergic the individual is to that certain food. Many of the "levels" are extrapolated from other foods and have not actually been individually calibrated; therefore the severity of allergy CANNOT be accurately measured by a blood test.

8. Food allergic individuals should carry 2 self-injectable epinephrine devices and antihistamine at all times in case of emergency. Self-injectable epinephrine devices should be renewed once a year.

The newer epipen injection devices are now coming in two-packs. They should NOT be split up. The two-packs are necessary because in 20% of anaphylactic reactions there will be a SECOND phase to the reaction necessitating a second epipen injection. Children should be monitored for 4-6 hours after the first injection to ensure another dose in not needed. Ideally, you will already have sought medical care in an appropriate setting by the time a second reaction occurs, but it is prudent to be prepared.

9. Epinephrine given for an allergic reaction is most effective when administered intramuscularly into the thigh muscle.  Corticosteroids are not useful in the acute management of an allergic reaction because of slow onset, but they might prevent biphasic or protracted reactions.

Corticosteroids are oral steroids that can be given by injection or orally (as a liquid or pill).

10. Adolescents and patients with a history of asthma are at higher risk for fatal anaphylaxis and require additional education. Delay of epinephrine is also a risk factor for fatal anaphylaxis.

Teenagers are at highest risk because they are most likely not to have their epipen when needed or they fail to understand how dangerous a food allergy truly can be.

11. Food allergies have a profound effect on quality of life, and support groups and Websites of food allergy organizations (such as the Food Allergy and Anaphylaxis Network, or FAAN) can be useful.

Food allergies can be a big deal and when they have been appropriately diagnosed by an experienced allergist, the child must be seen regularly and proper precautions must be taken. However, improper use of blood tests and skin tests can lead to restrictive lifestlyes and possibly create a food allergy when there was not one to begin with. As always, judicious use of tests at the appropriate time will lead to the best results and healthiest child.

1 comment:

Phoenix Family Medical Clinic said...

This is very interesting, thanks for sharing!