Retinol is the less-aggressive form of prescription-strength tretinoin and also has scientific evidence to prove its effectiveness. These creams are best started once every other night, a small amount used for the whole face. If too much is used, it increases irritation, not effectiveness. It’s important to use a moisturizer while the skin gets used to the retinol (usually takes about 2 weeks) as dryness can be a problem. Newer formulations of products have controlled delivery systems and special emollient ingredients to help reduce irritation. The use of a sunblock is mandatory in the morning because these products will make the skin slightly more sun sensitive.
Retinoids and retinols are best used at night because they are photo-inactivated, meaning direct sunlight will break them down and make them less effective. The most effective over-the-counter products contain 1% retinol (but no less than 0.5%).
As a prescription, I like tretinoin 0.05%. When I see patients in my practice, I typically get started with an over-the-counter retinol product, then slowly increase the strength over time until they are using a prescription.
There is no reason to be too aggressive at first because that may lead to excessive irritation and, many times, the person may stop using the cream (when all they really needed was a longer amount of time for their skin to get used to it). The best way to use retinoids is over years and decades!