The method
- Apply a small amount of the new product to the inner forearm or behind the ear
- Repeat once daily for two to three days on the same spot
- Watch for unusual redness, sharp stinging, persistent warmth, or small bumps
What it tells you
A clean patch test does not guarantee perfect facial comfort, because facial skin is thinner and routines are more complex. But an unhappy patch test is a useful early warning.
When it matters most
- First use of any retinoid, AHA/BHA, or vitamin C at high strength
- Skin that is easily unsettled by new formulas
- Products marketed as resurfacing, clarifying, or high-strength
Coyglow note: every Coyglow active page treats patch testing as step zero, not fine print.