Eczema-Like Psoriasiform Skin Reaction due to Brazilian Keratin Treatment.

The use of formaldehyde and formaldehyde releasers in hair-straightening formulations started in Rio de Janeiro in 2003. The technique is known as BKT, Brazilian keratin treatment. The aim of this study was to analyze the types of skin reactions presented by patients due to BKT. We describe 7 patients with severe erythema and scurf on the scalp which developed shortly after BKT. The lesions were eczema-like psoriasiform, located mainly on the scalp. Some patients also developed eczema-like lesions and pustules on the face, neck, upper arms, and upper trunk. Dermatoscopic findings included erythema, perifollicular and interfollicular scurf. The peripilar desquamation resembled the outer skin of an onion bulb. Scalp biopsies revealed psoriasiform and spongiotic psoriasiform patterns, one of them similar to anti-TNFα biologic drug psoriasiform alopecia. The possible consequences of the absorption of formaldehyde by hairdressers or clients are still to be verified by the scientific community; however, the skin and scalp reactions observed in our cases suggest a drug reaction phenomenon and not only eczemas of irritant or allergic origin.