I've received many questions about uncommon vegetable allergies. Here is what I found:
Q: I have a family member allergic to nuts. Are water chestnuts a nut or a fruit?
A: The Chinese water chestnut (Eleocharis dulcis) is an Asian vegetable, which is commonly used in Chinese food. The water chestnut is a misnomer as it is not a nut or even related to any nut species. Your family member is safe to eat them.
Q: I develop a rash from garlic. It takes two to four days to develop; my mouth dries up, my lips chap, and the skin over my eyes turns red and itchy. Is this at all a common allergy?
A: It’s not common. Garlic-related reactions include irritant contact dermatitis and allergic asthma and rhinitis (Am J Contact Dermat 1999 Mar;10(1):37-9.).
Q: I believe that I have developed an allergic reaction to pepper. It doesn't seem to matter if it's cooked or ground. Shortly after eating any food with pepper (usually within an hour) I get a sore throat. I'm finding it practically impossible to have meals without pepper hidden somewhere in the ingredients (ie: pizza, pasta sauce, packaged noodles, soup, even fresh deli meat seems to affect me). To make matters worse, I LOVE spicy foods and trying to avoid pepper is hard. Do you have any ideas about what I can do to combat this?
A: This is a difficult allergy and not common (Allergy 1998 Jan;53(1):36-41). You need to avoid pepper and, as you say, it's EVERYWHERE! Perhaps Internet chat rooms will have people with the same allergy and solutions.
Q: Avocados, bell peppers, bananas, cucumbers and cantaloupe make my mouth itch horribly but I eat them anyhow. My throat doesn’t swell but a cut on or in my mouth is awful! What can I do?
A: Protein in foods is usually the allergen (allergic-causing compound). With bananas and avocados, carbohydrates, not proteins, could be the source of cross-reaction between different plant allergens (Glycobiology 2001 Apr;11(4):261-74). The plants include mushroom, apple, asparagus, avocado, banana, carrot, celery, hazelnut, kiwi, onion, orange, pear, pignoli, strawberry, coconut, buckwheat, walnut, almond, pistachio, potato, tomato, legume, seed, pea, peanut, soybean and papaya. Cucumbers aren’t mentioned.
With cantaloupe, a study found foods associated with melon allergy are avocado, banana, kiwi, watermelon, and peach (J Allergy Clin Immunol 2000 Nov;106(5):968-72). Isolated melon allergy is rare.
One study (Allergy 1998;53(46 Suppl):52-4) found that bell pepper allergens could be a consequence of pollen allergy.
It seems you have many allergies going on at the same time. If your symptoms become unbearable, avoid those foods, not an easy task, and see your physician.
Q: I have an adverse reaction to onions. What is it about onions that cause the reaction/allergy. My sensitivity is often triggered simply by the sense of smell. My eyes do not water; instead I develop an intense headache, a minor swelling in the throat and become flush. These symptoms are alleviated shortly after departing from the vicinity of the onions. Raw onions in foods sometimes cause an immediate reaction. Cooked onions causes discomfort in the intestines. Sorry for the details, but this seems to be such an odd allergy - and one that is not socially well understood due to the prevalence of onions as "seasoning" and "garnishment" to many foods.
A: I have seen some research studies on allergy to onions. The most severe reactions were seen in one women who had intense itching, hives, skin eruptions, confusion, blurred vision, transient loss of consciousness, sweating and rapid heart beat after ingestion of raw or lightly-cooked onion. There were no problems with well-cooked onions. (Clin Exp Allergy 1995 Aug;25(8):698-703) One study showed that onion could lead to skin reactions on hands. (Contact Dermatitis 1987 Jan;16(1):11-20. ) Yet another study determined that the high levels of sulfites in Spanish pickled onions, and their low pH (3.3) would be responsible for asthmatic outbreaks (Clin Exp Allergy. 1995 Aug;25(8):680-1). Fortunately, onion allergy is rare. For those that have it, it is frustrating. As you say, onions are used everywhere. If you have a reaction to onions, you may need to cook your own meals to avoid them.
Q: My wife believes she is allergic to cauliflower. Whenever she has some she gets severe diarrhea and throws up. She has mentioned this to her doctor, who, believe it or not, laughed at her and told her that no one is allergic to cauliflower. She has since stopped going to him, but still the question lingers. Is it possible she is allergic to cauliflower?
A: I haven't seen anything on allergies to cauliflower yet I’ve seen much on other vegetable allergies (see above). However my older son throws up when he eats boiled carrots. Maybe they dislike the foods intensely, and react to them. The best is to avoid cauliflower, and find a sympathetic doctor.