Sunday Riley's A+ retinol serum initially caught my eye because it was advertised as an advanced strength retinoid that was suitable for both individuals with sensitive skin and experienced users of the ingredient that might be in search of a stronger product. The formulation contains a 6.5% retinoid blend, a relatively high percentage compared with other retinol products on the market.

The particular blend in question is composed of a retinoid ester, encapsulated retinol and retinol-alternative extracts derived from blue-green algae, all of which can impart the texture-improving wonders that retinol is known for, without overwhelming the skin and causing irritation. Additionally, an antioxidant known as COQ10 targets the appearance of sun damage while two different humectants soothe redness and draw moisture into the skin.