In a clinical trial conducted in 2021 by TIAN and his colleagues, 25 individuals with confirmed keratosis pilaris participated in the study. The subjects exhibited typical symptoms of keratosis pilaris on their limbs, including peri-follicular erythema (redness occurring around the hair follicle), papules, and pigmentation. They had not received any other treatment in the preceding six months.
The treatment involved the application of a high-concentration glycolic acid solution over four sessions, spaced 20 days apart, and during a five-year follow-up. The application protocol included concentrations of 50% glycolic acid for 5 minutes and 7 minutes, then increased to 70% for 5 minutes and 7 minutes, with treatments on days 0, 20, 40, and 60. Each application was followed by a neutralising solution to minimise irritation, and participants were advised to avoid sun exposure for a week after the treatment.
The evaluation criteria of the study included:
Counting the number of keratotic papules (on days 0, 20, 40, 60 and 80);
Measurement of the melanin and haemoglobin content in skin erythema and pigmentation of the hair follicle opening;
Measurement of skin clarity using a spectrophotometer;
Global Aesthetic Improvement Scale, which the patients used for self-assessment.
Over the course of 80 days, the results have been promising. The glycolic acid treatment reduced the number of keratotic bumps over time. By the end of the treatment cycle (day 80), the average number of keratotic papules decreased from 52.12 to 22.16, a reduction of approximately 58%. The melanin content, which affects pigmentation, and haemoglobin levels, related to redness, also showed significant changes, indicating an improvement in skin tone and less inflammation. Measures of skin clarity also improved, reflecting an overall enhancement in the appearance of the skin.
These results suggest that glycolic acid could be effective not only for alleviating the physical symptoms of keratosis pilaris, but also potentially improving the appearance of the skin by brightening it and reducing redness. However, the study indicated that although treatments with glycolic acid showed a reduction in symptoms during the treatment period, these effects were not maintained in the long term.
Five years post-treatment, follow-up evaluations revealed that the number of keratotic papules, melanin and haemoglobin content, and skin clarity had returned to levels observed prior to treatment. This suggests that the beneficial effects of glycolic acid may only be present during and immediately after treatment. Without ongoing use, symptoms of keratosis pilaris appear to gradually re-emerge, highlighting the potential need for continuous treatment management. Further studies would be required to confirm these findings and to explore long-term efficacy.