Many patients who have tree nut allergy wonder if they have coconut allergy as well. That goes more to the question, is coconut a tree nut? Coconut is actually a fruit, but the US FDA classifies coconut as a tree nut. There has been little guidance in patients with tree nut allergies on the safety of consuming coconut.
A study was done in assessing patients with coconut allergy and to see if they have co-sensitization to tree nuts. An apparent correlation between coconut and tree nut sensitization is mainly explained by sensitization to macadamia nut. The authors of the study plan to compare the IgE blood test results and to compare it with clinical symptoms.
Most patients allergic to tree nuts can safely consume coconuts, although this study seems to point towards a relationship specifically to macadamia nut allergy and coconut allergy.
Coconut allergy can be diagnosed by an allergy skin test or an allergy blood test by checking the IgE level to coconut. It is a relatively rare allergy with only a few reported cases in the literature. Coconut contact allergy is a more common route of allergy than ingesting it. There are many coconut derived products that are found in cosmetics, shampoos, soaps and detergents. Common names of coconut products are coconut diethanolamide, cocamide sulphate, cocamide DEA and CDEA. A coconut allergy rash may develop 1-2 days after using the product on your skin and it may take several days to resolve. If you do suspect coconut allergy contact an allergist or dermatologist who can do patch testing.
Overall though, a tree nut allergy does not have co-sensitization to coconuts, but based on this recent study, macadamia nut allergy may predict coconut sensitization. It remains to be seen if there is actually a clinical correlation between these two foods, or if there is just some cross reactivity on the skin test that does not actually imply real coconut allergy.