Apply three drops of La Roche-Posay Retinol B3 Serum in the evening onto previously clean and dry skin. If there is a feeling of discomfort on the skin during the first application, use the product with a lower frequency until the skin gets used to the action of Retinol. Keep in mind that when applying a product with Retinol it is also important to apply sunscreen in the morning to protect the skin from solar radiation.