LAUSR

Introduction: Hair straightening products like the Brazilian Keratin Treatment (BKT) contain high concentrations of formaldehyde, and its use is associated with adverse effects. In 2016, seven cases of eczema-like psoriasiform skin reaction secondary to BKT were described for the first time. We aim to investigate the clinical characteristics and dermatoscopic findings of patients with psoriasiform skin reactions due to BKT. Materials and Methods: A cross-sectional study was performed from October 2017 to June 2020. Patients who developed erythema and scales on the scalp following the use of BKT were included. Age, sex, number of BKTs, time elapsed between BKT and the skin reaction, pull test, and dermatoscopic findings were investigated. Descriptive and inferential statistics were used. Results: We found 43 patients with a mean age of 35 ± 10 years, predominantly females in 42 (98%) cases. The mean number of BKTs was 2 ± 2. The mean length of time elapsed to present the reaction was 12 ± 17 months and this was related to the number of BKTs (P = 0.01). The pull test was positive in 37 (86%) patients. The most frequent dermatoscopic findings were perifollicular scales in 42 (98%), red patches in 35 (81%), and peripilar desquamation resembling the outer skin of an onion bulb in 32 (74%). Conclusion: Hair straightening products are widely used and the psoriasiform skin reaction that develops afterward might be underdiagnosed. It is important to investigate the background of BKT in conjunction with the clinical and dermatoscopic findings suggestive of this cutaneous reaction.