Induction of Oral Tolerance in a Case of Severe Allergy to Coconut

Food allergy has increased in frequency in the last 2-3 decades. Some studies report a prevalence of up to 10% [1] depending on the study population (age range, dietary habits, allergen exposure, geographic location) and on the evaluation method used. In addition, more globalized dietary habits mean that it is increasingly frequent to find patients sensitized to allergens that are not part of traditional Western cuisine, such as coconut. Several cases of coconut allergy have been reported. Most were systemic reactions and anaphylaxis [2-7]. We present the case of a patient who underwent oral desensitization to treat coconut allergy. A 47-year-old Thai woman living in Tenerife (Canary Islands, Spain) was assessed at our unit for suspected coconut allergy. She had a previous history of severe allergic rhinoconjunctivitis and sensitization to house dust mite that were treated with specific immunotherapy, to which she responded well. The patient reported her first coconut allergy episode 4 years earlier. She presented with dysphonia, dyspnea, and palmoplantar pruritus immediately after eating grated coconut and subsequently reduced her intake of coconut, albeit not entirely. She occasionally experienced oropharyngeal pruritus after eating small amounts of coconut-containing foods, until she experienced a second episode of anaphylaxis with coconut milk curry and was referred to our unit. Skin tests were positive for commercial coconut extract (8 mm), Aroy-D coconut milk (8 mm), Dunn coconut milk (7 mm), and dehydrated coconut (8 mm) with a 4-mm histamine-induced wheal. Coconut-specific IgE measured using the ImmunoCAP System (Thermo Fisher) was 17.7 kUA/L. Oral challenge with coconut milk Aroy-D was not performed owing to positive results in the rub test, namely, palmoplantar and oral pruritus and dysphonia that required treatment with adrenaline. SDS-PAGE immunoblotting with coconut pulp extract and coconut milk extract was performed according to Laemli [8]. IgEbinding proteins of approximately 70 kDa, 66 kDa, 43/40 kDa, 26.5 kDa, 22 kDa, and 17 kDa were detected in coconut pulp extract, and bands of 45 kDa, 40 kDa, 37 kDa, 26 kDa, 24 kDa, and 20.5 kDa were revealed in coconut milk extract.