Formulation Degradation: Pink Color and Burnt Smell

Based on the change in color to pink and the development of a burnt smell, it indicates that your formulation has likely degraded.

Phenylethyl Resorcinol is an active ingredient known to be sensitive to stability issues. It can undergo oxidation, which often results in a pink or brownish discoloration. The unusual smell could also be a result of this chemical degradation or interactions between the ingredients in your specific formula.

Factors that can affect the stability of Phenylethyl Resorcinol include:

• The pH of the formulation (it is most stable in a pH range of 4-5).
• The presence of certain ingredients (such as amino acids or proteins; while Niacinamide is an amide, potential interactions should be considered).
• Exposure to light and air.

While you refrigerated the product, the initial mixing process or the formula composition itself might have contributed to the instability. A product that has changed color and developed an off-odor suggests that the active ingredients may no longer be effective, and there could be degradation byproducts present. Using a degraded product is not recommended as it may not provide the intended benefits and could potentially cause skin irritation or other adverse reactions.

Therefore, it is advisable to discard the product.