by Todd Green, M.D.

There has been a lot of recent coverage of food allergies and related issues both in the medical literature and popular press. With this attention many of the most common questions about food allergies are being asked and reviewed. It is encouraging that awareness of food allergies seems to continue to grow, but it is also apparent that some common myths and misconceptions, particularly around peanut allergy, remain. I will comment on some of these here. As we continue to discuss food allergies both among ourselves and also with friends, teachers, caregivers, and family members, shedding light on these issues will hopefully translate into wellness and safety for our children.

o Is there any such thing as a "mild" peanut allergy?

This is a very frequent topic of confusion. Individuals and their family members often assume that because prior reactions to ingestions only involved mild skin symptoms, for example, that future reactions will not involve anything more. Unfortunately we know from studies of serious reactions that the severity of a future reaction cannot be predicted from past reactions. While having a history of anaphylaxis definitely raises concern for a risk of anaphylaxis in the future, it is simply not safe to assume that reactions will remain mild just because they always have been.

o My son has peanut allergies and eczema. Should he be tested for other food allergies?

This is often not a straightforward question. There is some evidence that among children who have what physicians would classify as moderate to severe levels of eczema, about one-third or slightly more of these will have a food allergy that may be worsening their skin problems. Children with milder eczema do not seem to have food allergies as frequently, though this group has not been as well studied. Having peanut allergy increases a child's chance of having another food allergy, particularly to foods such as egg, cow's milk, and tree nuts, but this is not true in all cases. Often a child's history of food ingestions makes testing unnecessary. I encourage families in this situation to discuss the need for additional testing with their doctors.

o If my daughter has a peanut allergy, should she avoid tree nuts also? What about sesame?

We know that children with peanut allergy are more likely to have tree nut allergies as well. There is also often a significant risk of accidental exposure to peanut proteins in tree-nut containing foods, since often peanuts and tree nuts are processed on shared equipment. For these reasons many allergists recommend that peanut-allergic children avoid tree nuts as well. There may be exceptions to this among individuals who have regularly ingested tree nuts and not reacted to them, but even among this group it is extremely important to read labels and avoid any foods that may contain peanuts as well. This is another area where it is helpful to discuss your particular situation with your physician.
The question of what to do about sesame in peanut-allergic children is even more unclear and continues to evolve. Traditionally in the United States sesame has not been considered one of the major food allergens, and testing for sesame among nut-allergic children often seems to lead to "false positive" results, with a positive test not necessarily indicating that sesame cannot be safely ingested. The US Food Allergy Labeling and Consumer Protection Act, which took effect January 1, 2006, does not include sesame among the eight foods whose presence in a food product mandates clear labeling. Yet awareness of sesame allergy in this country and others is growing as our eating habits become increasingly internationalized, and agencies similar to the US Food and Drug Administration in Canada and Europe now include sesame among their most common list of food allergens. At this point there does not seem to be a clear answer to this question, though certainly if a child has been avoiding sesame because of concerns of allergy, it is worth discussing with a physician whether evaluation through testing or a food challenge may be indicated.

o My son has a peanut allergy. Can he be having a serious reaction with no hives? His last reaction was only gastrointestinal symptoms (stomach ache, & diarrhea ) but the doctor told us that we were lucky and we should have given the epi-pen.

Because skin symptoms such as hives, redness, and swelling, are most commonly associated with allergic reactions by many people, there is the sense among many that if there are not skin symptoms present then either there is not an allergic reaction or it is not a serious one. Unfortunately this can lead to a severe reaction being missed. In many of the most severe anaphylactic reactions (including fatal ones) skin symptoms are absent. This does not mean that not having hives means that the reaction is more severe, but it indicates that the lack of hives should not be taken as a sign that the reaction is not serious. If a peanut-allergic child has accidentally eaten peanuts and rapidly develops vomiting and trouble breathing, for example, epinephrine should be given even if there are no hives visible.

o My daughter has multiple food allergies including peanut which have been diagnosed by a board-certified allergist. She has had reactions to foods but never to peanut. Since she is now five years old, can we consider it unlikely that she will ever have a serious reaction to peanut since she has never had one in the past five years? Does she still need to carry the Epi-pen that the allergist prescribed?

This case speaks to the importance of the history in making decisions for food-allergic children. If this child has been eating peanuts regularly and not reacting to them, then the previous testing that was positive may indicate what is referred to as "sensitization" and not true clinical allergy. Many individuals, particularly allergic ones, will have positive skin or blood allergy tests to a food but can eat the food without a problem. It may also mean that she has outgrown her previous allergy, as about twenty percent of peanut-allergic children do. If, on the other hand, this child has never actually eaten peanuts, then the question is a little more complicated. I would not assume that just because she has not encountered peanuts accidentally that she will not in the future, particularly now that she is school-age and more likely to be encountering foods from people other than her immediate family. In this case it would likely be helpful to have the child re-evaluated by her allergist. If testing suggests a high likelihood that she is no longer allergic then attempting to reintroduce peanuts cautiously may be possible, but until the issue is resolved she should continue to have self-injectable epinephrine available to her at all times.

Todd D Green, MD is the Assistant Professor of Pediatrics in the Division of Pulmonary Medicine, Allergy and Immunology at Children’s Hospital of Pittsburgh.

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