Thank you for your inquiry.
You mentioned specifically sesame and coconut in regards to whether or not these two food entities should be avoided in children who have demonstrated allergy to peanut. I am not sure exactly why you chose these two examples, but I believe that there has been very little (if any) cross-reactivity exhibited between coconut and peanut.
Clearly anaphylaxis has been reported to coconut, and there has been some degree of reactivity reported between coconut and other foods (1-4). These include walnut and hazelnut. There also may be some weak correlation between coconut and latex allergy. Thus, foods that cross-react with latex such as banana, avocado, et cetera, may have some immunologic cross-reactivity with coconut, but no cross-reactivity has been demonstrated, at least to my knowledge, with peanut.
Sesame is a little different in that there has been some cross-reactivity between sesame and peanuts. Ara h 1 does have significant homology with Ses i 3 allergen of sesame seed. The question is, however, the importance of Ara h 1 in the production of anaphylaxis to peanuts. Nonetheless, there was a report of three patients who were previously sensitive to peanut who had demonstrated sesame allergy. It is not known whether this occurred because they were simply allergic individuals who were predisposed to develop allergies to many foods, or whether or not it existed because of the cross-reactivity mentioned above (5).
Based upon the comments above therefore, there would be, at least in my opinion, very little worry regarding coconut, but perhaps some concern regarding sesame. It is unknown, however, whether the simultaneous sensitization of patients to both peanut and sesame is simply related to the fact that they are highly atopic or due to a true cross-reactivity between allergens in these two foods.
It is normally my practice that if a child is eating a food without difficulty to let them continue to do so. I would not normally restrict a food based upon any potential cross-reactivity that they have ingested without difficulty. This would still be the case even if the child had a positive skin test to the food in question. For example, as we know, there is cross-reactivity between legumes in general (peanut being a legume), and many people have positive skin tests to peanuts and other beans, but eat beans without difficulty. I would not normally ask the family to restrict the ingestion of beans in this child.
Thus, neither the knowledge of cross-reactivity nor a positive skin test would, in my opinion, cause one to automatically eliminate a cross-reactive food if the child has been eating this food with any regularity without difficulty. Whether the continued ingestion of this food would prevent sensitization (e.g., as in the case of peanut-allergic children who become sensitized and continue to eat the peanut versus those who do not) or would cause sensitization, I do not believe we can answer that question with any confidence.
The issue that you described is somewhat different than the one that was dealt with by Dr. Sampson because of our knowledge of the fact that children who are allergic to peanuts are allergic to tree nuts, as you noted, in a large percentage of cases. This has been previously documented. This is not the case, to my knowledge, with either coconut or sesame, and I would assume that there is less likely to be accidental ingestion of either coconut or sesame in a peanut-allergic patient than there would be for the accidental ingestion of peanuts in tree-allergic patients due to the presence of the availability of mixed nut preparations. Also I think it would probably be less likely in regards to cross-contamination that occurs in factories.
Having given you my response, I would still like to get an opinion from someone who is truly an expert in this area. As you mentioned, Dr. Sampson has responded to a similar question in the past, and we would like to obtain his response to your question as well. He may be in disagreement with my suggestions, and if so, it would be wise for us to have that information. When I hear from Dr. Sampson, I will forward his response to you, but in the meantime, you will have my response for your perusal.
Thank you again for your inquiry.
1)Teuber SS, Peterson WR. Systemic allergic reaction to coconut (Cocos nucifera) in 2 subjects with hypersensitivity to tree nut and demonstration of cross-reactivity to legumin-like seed storage proteins: new coconut and walnut food allergens. J Allergy Clin Immunol 1999;103(6):1180-5
2)Nguyen SA, More DR, Whisman BA, Hagan LL. Cross-reactivity between coconut and hazelnut proteins in a patient with coconut anaphylaxis. Ann Allergy Asthma Immunol 2004;92(2):2814
3)Roux KH, Teuber SS, Sathe SK. Tree nut allergens. Int Arch Allergy Immunol 2003;131(4):234-44
4)Kim KT, Hussain H. Prevalence of food allergy in 137 latex-allergic patients. Allergy Asthma Proc 1999;20(2):95-7
5)Beausoleil JL, Spergel JM. Late diagnosis of tree nut and sesame allergy in patients previously sensitized but tolerant to peanut. Ann Allergy Asthma Immunol 2006;97(4):443-5
Phil Lieberman, M.D.
We have received a response from Dr. Sampson. Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.
Response from Dr. Hugh Sampson:
I agree with your recommendations. I would not eliminate a food that someone is eating, regardless of the skin test or allergen-specific IgE. In my experience, coconut allergy is quite uncommon and we do not routinely restrict coconut from the diets of peanut allergic patients for the reasons that you discussed. Like you, I am not sure whether there is true clinical cross-reactivity between peanut and sesame, or whether the relatively few individuals who are allergic to both are just highly allergic and develop allergy to both. Unless a child is highly allergic and/or has a history that raises a question about possible allergy to sesame, I wouldn't automatically restrict sesame from the diet of a peanut-allergic child. I did insert a couple words in red for you to consider.
All the best,