A histological comparison of 50% and 70% glycolic acid peels using solutions with various pHs.

BACKGROUND

Seventy percent glycolic acid solutions are being commonly used as superficial chemical peeling agents. The pH of these solutions ranges from 0.08 to 2.75. The histologic effects of these various pH solutions on human skin have not been studied.

OBJECTIVE

The histologic effects of several commercially available glycolic acid solutions at various pHs were examined.

METHODS

Test areas of seven glycolic acid solutions were applied to facial skin of two patients. The skin was not prepped for a peel prior to the application of the acid. The solution was left in place for 30 minutes, then neutralized. After 48 hours, a 2-mm punch biopsy was performed and examined histologically.

RESULTS

The peeling solutions with a pH below 2 demonstrated the potential to induce crusting and necrosis, which was not seen with the partially neutralized solutions with a pH above 2. The higher concentration acids (70%) created more tissue damage than the lower concentration (50%) when comparing solutions with free acid.

CONCLUSION

This study demonstrates that chemical peeling with a 70% free glycolic acid creates more tissue damage than a free glycolic acid. When using a 70% glycolic acid solution, the lower pH products (below pH 2) create more necrosis than the partially neutralized products with a pH above 2. At this time there is no evidence that creating necrosis leads to a more favorable result of the peel. Therefore, the use of partially neutralized glycolic acid solutions seems prudent, since they have a better safety profile than low pH solutions, which contain only free glycolic acid.