Retin A is the most effective form of topical treatment for acne. Retin A can also be used for various skin conditions such as eczema, melasma, PIH, rosacea, Psoriasis and skin hyperpigmentation issues. Retin A works by exfoliating the skin and boosting the production of collagen in the skin. Retin A makes the skin soft and thin which in turn can make it very sensitive to sun rays and harsh chemicals. Retin A sunscreen combo is necessary when using retin a to avoid further damage to the skin. Side Effects of Retin A It can cause skin redness. It can cause skin flaking. It can cause skin inflammation. It can cause irritability. It can cause ear irritation. It can cause burning sensations. It can cause sun burn. It can cause headache. It can cause PIH scar.