Ferdman et al note that inhalation of pectin has been identified as a cause of occupational asthma but that allergic reactions to ingested pectin have previously not been reported.
They then provide details of a young boy who developed anaphylaxis, once after eating cashews and later after eating a pectin-containing fruit "smoothie." He also has a history of generalized itching after eating grapefruit.
Skin tests or radioallergosorbent tests (RASTs) were performed using pectin and other suspected food allergens. They found that the boy had a positive skin prick test reaction to pectin and a high RAST reaction to cashew and pistachio. He had a low-level positive RAST reaction to grapefruit.
The pectin in the smoothie was confirmed to be of citrus origin and their review of previous case reports of pectin-induced occupational asthma revealed several cases of allergies to and cross-reactivity with cashew.
They conclude that:
- eating pectin in susceptible individual can cause hypersensitivity reactions;
- cashew, and possibly pistachio, allergy may be associated with pectin allergy, and
- that the possibility of pectin allergy should be considered in cashew- or pistachio-allergic patients who have unexplained allergic reactions.
Ferdman RM, Ong PY, Church JA. Pectin anaphylaxis and possible association with cashew allergy. Ann Allergy Asthma Immunol. 2006 Dec;97(6):759-60.