Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at NSU
A 5-year-old boy had facial rash after consumption of coconut cookie on two occasions. He has been avoiding that type of cookie since then. He no history of eczema, asthma or allergic rhinitis.
Family history is positive for father with allergy to shellfish and sunflower seeds.
He is not on any medications on a consistent basis. No known drug allergies
Physical examination is normal.
What would you suggest for diagnostic testing?
He had skin prick testing with limited panel of environmental allergens and a comprehensive panel of food allergens which included the 8 food allergen groups, implicated in more than 90% of food allergic reactions. He had borderline reactions to banana. Otherwise, the skin test was negative for cat, dog, cockroach, dust mite, mold mix, trees, and also negative for peanuts, tree nuts, egg, milk, fish, shellfish, soy, wheat, and sesame. We did not have coconut for skin testing, but that was added to the serum IgE testing.
What is the most likely diagnosis?
This patient has a suspected food allergy to tree nuts, in particular coconut, but the negative skin test makes the likelihood of clinical food allergy lower.
What is the next step in the management?
EpiPen was prescribed to be used in case of anaphylactic reaction. They were educated on the EpiPen use and we provided the link to teaching videos on our website.
Serum IgE testing for tree nuts, peanut, and coconut was ordered. The laboratory results are available show low normal total IgE of 10 kUA/l (low normal), negative sIgE (<0.10) for coconut, tree nuts, peanut, fish, shellfish, banana, and dust mite.
Diagnosis: Reported urticaria with with coconut cookie, with negative skin and blood test; oral food challenge was suggested to rule out food allergy
What happened next?
The combination of clinical history, skin prick test and blood test makes food allergy to coconut unlikely. This conclusion needs to be verified with oral food challenge in the allergy clinic.
Final diagnosis: A month later, the patient had an oral food challenge with the coconut cookie that was negative. Food allergy to coconut was ruled out. The cause of hives remained unclear.
Oral Food Challenges (click to enlarge the diagram).
Food Allergy: Brief Review
Food Allergen Avoidance
Food Challenges for Diagnosis of Food Allergy