Colostrum

Colostrum (typically bovine-derived) is used in leave-on skincare for its proteins, lipids, and growth factors, often at low percentages but as a complex biologic mixture rather than a single inert compound. While it isn’t a classic irritant like acids or retinoids, complex animal-derived proteins can provoke stinging or inflammatory reactions in reactive/eczema-prone skin and pose a non-trivial allergy/sensitization risk, especially on impaired barriers. Given the variability of extracts and the potential for delayed hypersensitivity in sensitive populations, I rate it as moderate and recommend patch testing. Safety Notes: In mass-market leave-on creams/serums, bovine colostrum (often listed as Colostrum, Colostrum Powder, or Hydrolyzed Colostrum) is commonly used at low “label claim” levels around 0.05–1% due to cost, odor/color impact, and protein stability constraints. Specialty/niche consumer products marketed as “colostrum creams/serums” and some bar soaps can use much higher loads, with concentrated anhydrous or emulsion bases incorporating roughly 5–20% colostrum powder/extract equivalents (higher levels are uncommon because of viscosity, microbial risk in aqueous systems, and sensory instability). No specific EU/FDA cosmetic concentration limits are established for colostrum itself; practical formulation limits typically govern, and rinse-off products may tolerate somewhat higher apparent percentages than leave-on due to lower exposure time.