Allergic reactions to garlic have also been reported in the literature. Garlic allergy can manifest as occupational asthma, contact dermatitis, urticaria, angioedema, rhinitis, and diarrhea. A 35-year-old woman experienced several episodes of urticaria and angioedema associated with ingestion of raw or cooked garlic, as well as urticaria from touching garlic. Two garlic extracts as well as fresh garlic produced a 4+ reaction on skin prick tests (SPTs) in this patient, but no other food allergens produced positive results. The patient's symptoms were immunoglobulin E (IgE)-mediated, but she also produced specific IgG, which confounded the results of IgE testing (90). A group of 12 garlic workers with respiratory symptoms associated with garlic exposure underwent SPTs using garlic powder in saline, commercial garlic extract, and various other possible allergens; bronchial provocation tests with garlic powder; oral challenge with garlic dust; and specific IgE testing using the CAP (CAP System; Pharmacia, Uppsala, Sweden) methodology. Patients were classified into two groups depending on the results of the bronchial provocation tests. Seven patients had positive responses (rhinitis or asthma) to the inhalation challenge test, and were designated as Group 1. Six of these patients reacted to the garlic SPT, and five had specific garlic IgE. In addition, six patients had specific IgE to onion, three to leeks, and four to asparagus. In Group 2 (patients who did not respond to the inhalation challenge), one patient had a positive response to the garlic SPT, one to the onion SPT, and two to the leek SPT. None had garlic or onion IgE. Three patients in Group 1 reported that in the past, they had experienced urticaria, asthma, angioedema, and ana-phylaxis after garlic ingestion. Two of these patients were administered garlic orally in increasing doses up to 1600 mg. The patient who had reported anaphylaxis tolerated the full dose, whereas the patient who reported urti caria developed a 35% decrease in forced expiratory volume in 1 second (FEV1) and angioedema of the eyelids at a dose of 500 mg. Using immunoblot and IgE immunoblot inhibition analysis, the investigators also attempted to elucidate the specific garlic component to which the patients reacted. Using pooled sera from Group 1, the investigators found that several garlic allergens cross-react with grass and Chenopodiaceaepollens (91).
A group of 50 catering workers with eczema or dermatitis of the hand or arm were studied for suspected occupational dermatitis. All workers were prick tested with foods that commonly irritated their hands at work, as well as patch tested with garlic 50% in arachis oil, onion 50% in arachis oil, and pieces of the same prick test foods. Seven workers reacted to 50% garlic in oil and one reacted to whole garlic (92).
Housewives were found to be more likely to experience contact dermatitis of the hand than those exposed to garlic in other job settings such as chef, agricultural, and industrial positions. A group of 93 patients were patch tested with diallyl disulfide. Of these, 22.6% tested positive for allergy, 79.5% of whom were women. Dermatological eruptions were primarily located on the hand; however, lesions were also seen on the feet, head, legs, and in widespread distribution (93).
Other cases of occupational allergy and asthma associated with garlic extract include an 11-year-old boy who helped with garlic harvesting on his parents' farm and a 15-year-old who helped collect and store garlic (94); a 49-year-old proprietor of a spice marketing and packing firm (95); a 30-year-old electrician working in a spice processing plant (96); and a 16-year-old who had helped his father load stored garlic into a van for several years (97). Symptoms described included wheezing (95); cough, dyspnea, and chest tightness (96); rhinitis (94,95,97); and conjunctivitis (94). Garlic allergy was confirmed using a wide variety of tests including scratch testing (94); SPT (95-97); IgE to garlic using radioallegosorbent test (RAST) (96), polystyrene tube solid phase radioimmunoassay technique (95), CAP system (97); oral challenge (96); bronchial provocation (94-97); and basophil degranulation (94). Test methodologies are detailed in the references cited. Patients with occupational garlic allergy are often allergic to other foods as well as to airborne allergens, including peanuts, onion, ragweed pollen (95), asparagus, and chives (96).
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