Using Glycolic Acid (AHA) in Formulations

Regarding the use of Glycolic Acid at a concentration not exceeding 5% in face and body cream formulations for exfoliating purposes (melasma, dark spots, scars):

1. Can it be used during the day and exposed to the sun normally?
   Using products containing Glycolic Acid during the day is possible, but it is crucial to understand that AHAs like Glycolic Acid increase the skin's sensitivity to the sun. Therefore, if you use a formula with Glycolic Acid during the day, you must apply a broad-spectrum sunscreen with sufficient SPF daily. Normal sun exposure without adequate protection is not recommended and can lead to sunburn, increased pigmentation, or other sun damage.

2. Should it only be used at night?
   Using Glycolic Acid products at night is generally recommended. This minimizes the risk associated with increased sun sensitivity during peak daylight hours and aligns with the skin's natural repair process that occurs overnight.

3. Is a concentration of 2-3% sufficient for exfoliating purposes to target melasma, dark spots, and scars?
   A concentration of 2-3% Glycolic Acid can be effective for gentle exfoliation and improving the appearance of melasma, dark spots, and scars over time, especially with consistent use. The efficacy also depends significantly on the pH of the final formulation. For optimal results, the pH should ideally be below 4.0, and even better below 3.5, as the activity of Glycolic Acid is highly dependent on pH. While 2-3% is a good starting point, higher concentrations (often above 5%) are typically used under professional supervision for more intensive treatment of these concerns. Products like Glycopure™, Ampho-Glycolic™, and ActiveRelease™ Glycolic Acid are examples of Glycolic Acid sources that can be used in formulations, each with specific characteristics regarding purity, irritation potential, and release mechanisms.

In summary, while daytime use is possible with strict sun protection, nighttime application is generally preferred. A 2-3% concentration can be effective for gradual improvement, but the final pH of the product is critical for its performance.