Whey Protein

Whey protein is used topically mainly as a conditioning/film-forming ingredient, typically at low percentages, and it is not inherently caustic or pH-dependent. However, as an animal-derived protein it can provoke contact reactions (including in highly atopic individuals) via protein sensitivity, and protein-containing cosmetics have documented potential for irritation or allergic contact dermatitis in a small but meaningful subset. Given the stakes for eczema-prone and compromised skin, I score it as mild rather than gentle to reflect that occasional sensitivity is plausible even at typical concentrations. Safety Notes: In commercial skincare, whey protein (often listed as Whey Protein, Hydrolyzed Whey Protein, or Whey Amino Acids) is frequently used at very low levels (about 0.01–0.5%) in leave-on creams/serums and rinse-off cleansers primarily for conditioning, film-forming, and marketing positioning. Higher-strength consumer-available products (e.g., protein hair/skin masks, body butters, and specialty “protein” treatments sold OTC) can reach ~1–5%, and a small number of anhydrous or mask-style formulations formulated around protein/peptide actives have been observed up to ~10% where odor, solubility, stability, and tack become limiting.