Clinical outcomes and 5-year follow-up results of keratosis pilaris treated by a high concentration of glycolic acid

Background: Keratosis pilaris is a hereditary abnormal keratosis of the hair follicle orifice. Gray-brown keratotic plugs in the pores and dark red keratotic papules at the openings of hair follicles can be seen, which contain coiled hair and are often accompanied by perifollicular erythema and pigmentation. Glycolic acid can correct the abnormalities of hair follicular duct keratosis and eliminate excessive accumulation of keratinocytes. It also promotes skin metabolism and accelerates the melanin metabolism. The therapeutic effect is related to the glycolic acid concentration.

Aim: To evaluate the efficacy and safety of a high concentration of glycolic acid in the treatment of keratosis pilaris, and to observe the outcomes at 5-year of follow-up.

Methods: Twenty-five participants were recruited and areas with typical keratosis pilaris were selected as testing sites. High concentrations of glycolic acid (50% or 70%) were applied to a circular area (d = 8 cm, S = 50 cm²) and repeated four times, on days 0, 20, 40 and 60. Before each treatment and 20 d after the last treatment, on days 0, 20, 40, 60, and 80 and at a 5-year follow-up, The number of follicular keratotic papules were counted and the extent of perifollicular erythema and pigmentation was determined. At the same time, the participants provided subjective evaluations of treatment efficacy and safety.

Results: Treatment effectiveness was indicated by the percentage of keratotic papules in the test site, on days 20, 40, 60 and 80, which were 8%, 12%, 36%, and 60%, respectively. Compared with day 0, each difference was significant (P < 0.05). Compared with day 0, differences in melanin content (M) in the skin and skin lightness (L) on days 40, 60 and 80, the were statistically significant (P < 0.05); skin hemoglobin content (E) on days 60 and 80 was statistically different as compared with before treatment (P < 0.05). There were no significant differences in the number of keratotic papules, M, L, and E in 9 participants at the 5-year follow-up compared with before treatment (P > 0.05%).

Conclusion: A high concentration of glycolic acid significantly improved skin roughness as well as follicular hyperpigmentation of patients with keratosis pilaris. The treatment was relatively safe, but there was no significant difference at the 5-year follow-up compared to before treatment.