Article in English: Retin-A products are typically applied at night, as the vitamin-A compounds they contain are photosensitive and will make your skin much more sensitive to sunlight. Applying the product at night also gives it a chance to absorb into the skin fully.  If you do decide to apply Retin-A products during the daytime, make sure you apply a sunblock afterward and keep out of direct sunlight as much as possible. Also double-check that your chosen product won't break down when exposed to sunlight; while most newer formulas stay intact, many older formulas do not.  When you begin Retin-A treatment, your doctor will probably recommend that you only apply it every two to three nights. This will give your skin a chance to adjust to the cream and help to avoid irritation. Once your skin has adjusted, you can build up to using it every night. Apply the Retin-A to dry skin, about 20 minutes after thoroughly cleansing your face. Retin-A is a very strong treatment, so it imperative that you use it correctly and only apply it in very small amounts.  At most, a pea-sized amount of cream should be used on the face, and a little more if applying to the neck. A good technique is to dab the cream on the areas most affected by wrinkles, age spots, etc., then wipe any remaining cream over the rest of the face. Many people become scared of using Retin-A because they start applying the cream too heavily and experience negative side effects such as dryness, irritation, stinging and acne outbreaks. However, these effects can be greatly reduced if the cream is applied in moderation. Due to the drying effects of Retin-A treatments, it is imperative that you always wear a hydrating moisturizer, day and night.  At night, wait 20 minutes for the Retin-A to be fully absorbed into the skin, then apply your moisturizer. In the morning, wash your face thoroughly before applying a second moisturizer containing a high SPF. Sometimes, it can be hard to spread the recommended pea-sized amount of Retin-A to all of the areas of the face where it's...

Summary in Vietnamese:
Chỉ sử dụng các sản phẩm Retin-A vào ban đêm. Chỉ sử dụng một lượng nhỏ Retin-A. Luôn sử dụng kết hợp với kem dưỡng ẩm. Xử lý tình trạng nhạy cảm và kích ứng. Chờ một thời gian để kem có tác dụng.