Great question and the most commonly asked by retinoids users (or soon to be users :)! 

Most people start to see the benefit of daily retinoid use around 6 weeks. If used every 2-3 days, then the benefit would take around 10 weeks to see.  If only used once weekly, it may take up to 3 months to see the benefit.  

For the first 2-4 weeks of retinoid use, the skin is undergoing many changes- dry, rough cells are being exfoliated, oil glands are shrinking, collagen is remodeling and a whole host of skin proteins and enzymes are being activated.  This is when there can be mild dryness or flaking or even a slight uptick in acne, all of which resolve quickly with continued use of the product. Patience is the name of the game here, and great results take time as the skin acclimates to the retinoid.

After 4-6 weeks, the skin will get used to tretinoin and will begin to be noticeably smoother and more even. A lot of the initial irritation will settle down and true “retinization” of the skin is in full force.  

12 weeks (or 3 months) marks a turning point in the process.  If you were to put the skin under a microscope (which is what is actually done in skin studies), you would see a new zone of actively repairing collagen that stretches the skin taut and reduces fine lines.  Individual skin cells would appear more organized and oil glands and pores will be smaller.  

At 6 months, the skin continues to improve with new collagen in place and fresh blood vessels to bring in skin nutrients.  Looking at the skin, it would appear more smooth and firm.

At a year, the skin continues to maintain new collagen and smaller pores, in addition to more improvement in tone and pigment due to decrease melanin synthesis.  

Many wonder if the benefits of tretinoin persist long term.  The answer is that yes, tretinoin use will benefit the skin in the long run, but that requires persistent and ongoing tretinoin use.  The skin turns over in about a month, so if tretinoin use is stopped for a month or more, the skin will again take time to acclimate to the product.  The benefits of tretinoin will persist for longer than a month, but will not be as sustained or effective without continued use.  

Tretinoin use is one part of a skin system, and for some who have already had significant sun exposure or other skin conditions, the skin can still develop fine lines and wrinkles.  Consistent retinoid use, however, can help to slow down this process and promote healthy skin. To read more about Tretinoin, read our ultimate guide to Tretinoin.