Anaphylaxis to apple: is fasting a risk factor for LTP-allergic patients?

BACKGROUND Primary apple allergy is frequent in Mediterranean countries where hypersensitivity to lipid transfer protein (LTP) is common. Due to its stability upon pepsin digestion, LTP may cause systemic allergic reactions. This study investigated the potential risk associated with an isolated intake of apple while fasting in LTP-hypersensitive patients with clinical allergy to peach but not to apple. PATIENTS AND METHODS Based on the observation of 6 patients who experienced 7 apple-induced anaphylactic reactions that in 6 cases followed the ingestion of the fruit after fasting, open food challenges were carried out in 12 patients LTP-hypersensitive patients with peach allergy but tolerant to apple. RESULTS Four out of the 12 patients (33%) reacted to apple upon oral challenge. CONCLUSION Fasting seems to play a relevant role in the clinical expression of allergy to LTP. It is possible that in an empty gastrointestinal tract the allergen is absorbed more rapidly. Alternatively, pepsin might digest the food matrix more efficiently, thus increasing the concentration of the purified allergen that comes in contact with the gut mucosa.