Ingredient That May Cause White Residue on Acne in Pathummas Clay Mask

Sulfur is a common ingredient used in acne treatment products, including clay masks like Pathummas. It helps to reduce oiliness, exfoliate dead skin cells, and has antibacterial properties, which are beneficial for treating acne. Sometimes, products containing sulfur can leave a white or light yellow residue on the skin as they dry.

An example of a water-soluble sulfur compound used in cosmetics is BioSulphur™ EQ (Ichthammol). While the specific formulation of Pathummas clay mask is proprietary, sulfur or sulfur compounds are highly likely candidates for the ingredient causing the white residue you observed on acne spots.