Photoallergic contact dermatitis in a pig farmer, caused by cotrimoxazole

ARTICLE

Auteur(s) : Tessin Watanabe, Hiromi Higaki, Nanako Yamada, Yuichi Yoshida, Osamu Yamamoto

Division of Dermatology, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago 683-8503, Japan

Several antibiotics and growth promoters are used widely in pig farming. They rarely cause allergic or photoallergic contact dermatitis [1-3]. We describe a case of photoallergic contact dermatitis in a pig farmer, caused by cotrimoxazole.

A 53-year-old man, with no atopic history, had a 1-year history of skin lesions on his face, neck, ears, forearms and dorsal hands. He had been working as a pig farmer for the past 20 years and had used oxytetracycline, tylosin and cotrimoxazole (sulfamethoxazole-trimethoprim) for preventing infectious diseases in pigs. He handled dry pig foods containing these drugs without using protective clothing or gloves for 2 months before the development of skin lesions. The pattern developed was lichenified erythema on sun-exposed areas, including his forehead, cheeks, neck, ears, forearms and hands (figure 1). Topical steroids were ineffective for treating these lesions. Blood biochemistry was within normal limits. Histopathologically, the cutaneous lesions of his dorsal hand showed hyperkeratosis, acanthosis and superficial perivascular lymphocyte infiltration. His skin lesions improved slightly but became worse again. We suspected that the lesions were caused by contact or photocontact allergy to the antibiotic used in pig feed. Minimal erythema doses for UVA and UVB of the patient were within normal ranges. Patch testing was performed with oxytetracycline, tylosin and cotrimoxazole at 1% and 10% in petrolatum. The patch testing only yielded positive reactions for tylosin at 1% and 10% (++), both at D3 and D4. Photopatch tests using oxytetracycline and cotrimoxazole with 5 J/cm₂ UVA were also performed at the same concentrations as those used in patch testing. Positive results were obtained with cotrimoxazole at 10% (+) at D3 and D4. Drug-induced lymphocyte stimulating tests (DLST) revealed positive reactions to tylosin with a stimulating index of 431% and to cotrimoxazole with a stimulating index of 213% (normal < 180%). The skin lesions improved with topical steroid treatment after hospitalization for tests. Therefore, we advised the patient to avoid handling these antibiotics in the future.

Based on the clinical history, positive DLST index and positive results of patch and photopatch tests, we made a diagnosis of allergic contact dermatitis to tylosin and photoallergic contact dermatis due to cotrimoxazole. In the present case, both allergic contact dermatitis to tylosin and photoallergic contact dermatis due to cotrimoxazole in a pig farmer were demonstrated.

Tylosin and Olaquindox are well-known contact allergens for pig farmers. Fixed drug eruptions and toxic epidermal necrolysis have been reported as adverse skin reaction to cotrimoxazole [4, 5]. However, photoallergic skin reactions to cotrimoxazole (sulfamides) are extremely rare [6]. In addition, photoallergic contact dermatitis due to cotrimoxazole in a pig farmer has not been reported as far as we know. A persistent dermatitis of sun-exposed areas in a pig farmer should be studied as a possible photoallergic contact dermatitis, possibly induced by antibiotics.

Acknowledgements

References

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