Is it safe for me (20 y) to begin using Retin-A .025% to prevent wrinkles?

Thank you for your question. Tretinoin cream can be used in patients as young as 12 for acne, but a long term benefit is prevention of fine lines and wrinkles as you mentioned. Tretinoin can be safely used long term as long as there are no side effects and you are not trying to get pregnant. I highly recommend you consult with a board certified dermatologist to have your skin evaluated and to discuss appropriate treatment options. Take care and good luck.

Age doesn't really matter when it comes to topical products so you aren't too young to start, however retin-a is stronger than retinol so it may cause irritation, especially if used too frequently. Retinoids exfoliate the skin so you don't want to use it more than 3-4 times a week. You can start with the retin-a and see if it causes any irritation and if it does you can try using it only once or twice a week or you can switch to retinol to see if that causes any irritation.