Azelaic acid is a dicarboxylic acid that addresses visible redness, post-blemish marks, and congestion simultaneously — with an unusually gentle profile for an 'acid'.
Prescription literature at 15–20% establishes its rosacea and hyperpigmentation credentials; cosmetic 10% versions support tone.
How to use: Morning or evening; layers under SPF beautifully.
Cautions: A brief tingling on first week of use is common and transient.