Coconut contact urticaria and specific-IgE
I saw a 28 year-old patient who developed hives on the arm 10 minutes after applying a lotion containing coconut. Prick testing with coconut was 5mm positive. Can I assume that she is allergic to coconut and does she require an automatic epinephrine injector? I might add that she is also atopic.
In my opinion the patient would likely experience a systemic reaction to coconut with ingestion. I assume there is no history of ingestion without reaction as ingestion is the ultimate assessment of food allergy. I would prescribe an epinephrine autoinjector and avoid topical use of coconut containing products. Most of the topical reactions to coconut are cell mediated but IgE mediated topical reactions have been reported (1,2).
I have shard your question with Dr. Scott Sicherer at the Jaffe Food Allergy Institute, Icahn School of Medicine. His comments are below.
There is an entity called “Contact urticaria” where skin contact results in hives but the food can be ingested without a reaction. We see this often in babies who get a few hives around the mouth from direct contact with a food while eating but no other symptoms from ingestion. Another way to look at this is that we know people can be “sensitized” (positive skin test) to a food but tolerate ingestion. So getting hives from skin contact is similar to a skin test. Thus, the evaluation has to consider if she has been eating coconut. One could argue that if she has been fine eating coconut there is no reason to stop her from eating it. If she has symptoms from eating coconut and no longer eats it, then you have probably simply confirmed a coconut allergy. If her ingestion history is not sufficient to make a decision, a supervised oral food challenge may be needed.
1. Lakshmi, Chembolli. "Allergic Contact Dermatitis (type IV hypersensitivity) and type I hypersensitivity following aromatherapy with ayurvedic oils (Dhanwantharam thailam, Eladi coconut oil) presenting as generalized erythema and pruritus with flexural eczema." Indian journal of dermatology 59.3 (2014): 283.
2. Aalto‐Korte, Kristiina, et al. "Occupational allergic contact dermatitis caused by coconut fatty acids diethanolamide." Contact dermatitis 70.3 (2014): 169-174.
I hope this information is of help to you and your practice.
All my best.
Dennis K. Ledford, MD, FAAAAI