Garlic (Allium sativum) is a vegetable of the Alliaceae family and is used as not only a spice but also a folk remedy for various illnesses such as asthma, fever and eruptions.1 Adverse reactions of naturopathic medicine, such as chemical burns and allergic contact dermatitis resulting from topical treatment with crushed raw garlic, are well documented.1 We present a case of garlic-induced irritant contact dermatitis caused by peeling of garlic bulbs; this case was clinically similar to a case of nail psoriasis.
A 64-year-old woman presented with severe erythematous rashes on all the fingertips of both hands. She had peeled many bulbs of garlic with bare hands 1 month before presentation. Pruritic lesions appeared on the fingertips the next day and progressed to hyperkeratosis and fissuring on the subungual areas. Physical examination revealed crusted and erosive erythematous lesions distributed mainly on the subungual skin of all fingers and distorted nail plates with subungual hyperkeratosis and hemorrhage (Fig. 1a,b). Other regions, including her toes, were intact, and routine laboratory investigations showed no abnormalities. The result of specific immunoglobulin (Ig)E radioallergosorbent test (RAST) for garlic was negative. An incisional biopsy specimen was obtained from the erythematous lesion. Histopathological examination showed a superficial dermal and perivascular infiltrate of lymphocytes with hyperkeratosis and irregular acanthosis; neither spongiform pustules of Kogoj nor band-like inflammatory cell infiltrates were found (Fig. 1c). The patch test result for diallyl disulfide, which is known as the main allergen of garlic responsible for allergic contact dermatitis,2 was negative. We diagnosed garlic-induced irritant contact dermatitis. She was advised to avoid contact with garlic and was treated with a local corticosteroid ointment. Although the erythematous lesions persisted for more than 3 months, the nail deformity resolved completely within 1 year (Fig. 2a–c).
Garlic is known to cause various dermatoses. Allergic contact dermatitis is considered to be mainly due to diallyl disulfide, the strongest sensitizing compound in garlic,2 and typically produces hand dermatitis in cooks, food handlers and housewives.3 In a recent study, four of 13 curry chefs with hand dermatitis had a positive patch test result for diallyl disulphide, although all 13 housewives and others had a negative result.4 Other garlic-induced rashes include irritant contact dermatitis, known as garlic burn. Garlic may also elicit acantholysis and can cause a pemphigus vulgaris-like eruption in genetically susceptible individuals.3 In contrast, the irritant reactions of garlic have been used for the treatment of warts.5 Aqueous garlic extract was applied twice daily on warts in 23 patients, and complete recovery was obtained in all cases after 1–2 weeks of treatment.5 However, this treatment produced blisters, redness, burning and hyperpigmentation around the application area.5 Patch testing with 10% water extract of garlic showed irritant reactions in six of 43 patients; among all the tested vegetables, garlic showed irritant reactions in the highest number of individuals.6 Nevertheless, the reasons for the application of garlic as a naturopathic remedy are divided into two groups: (i) crushed garlic is applied to the skin of various sites because of fever or an acute asthmatic attack, and (ii) it is applied locally over the site of the complaint such as eruptions and pain.7
To the best of our knowledge, no study has reported a case of irritant contact dermatitis induced by peeling of garlic bulbs. Furthermore, this patient showed severe inflammation on the fingertips: this resembled nail psoriasis, which affects up to 55% of patients with psoriasis.8 Unlike the common garlic burn caused by the application of crushed raw garlic, the insertion of a part of the peel or garlic into the hyponychium resulted in long-term, severe inflammation in the subungual regions. Subsequent subungual hyperkeratosis followed by complete recovery highlighted the importance of avoiding the considerable causal factors. Dermatologists occasionally encounter patients with distal onycholysis and marked subungual hyperkeratosis of hands, but not onychomycosis. The nail deformity is considered to be induced by dermatitis of the proximal nail fold and hyponychium, although the cause remains undetermined in many cases. It is important that housewives and chefs with hand dermatitis and subungual hyperkeratosis thoroughly avoid contact with Alliaceae vegetables, such as garlic, onion, chives, shallot and leek, with bare hands.