Warning: Retinol 1.0 is only intended for those who already have experience with Retinol 0.5. Retinol 1.0 is a very high strength retinol product, and should only be used in the evening. To avoid irritating the skin, use a lipid-rich moisturiser such as Triple Lipid Restore 2:4:2 Anti Ageing Moisturiser after application of the 1.0 retinol to seal in moisture. SkinCeuticals recommends you consult a skincare professional before starting use of a product with this high a concentration of retinol. Retinol increases skin cell turnover and this process makes the skin extra sensitive to the effects of the sun. It's essential to use a broad spectrum, high SPF sunscreen such as Skinceuticals Ultra Facial Defense SPF50 when using this retinol product.