What is Retin-A?
Retin-A, also known as tretinoin, is a naturally occurring vitamin A that is used topically in the treatment of acne.  The active ingredient tretinoin penetrates beneath the skin and is able to loosen and decrease the cohesiveness of follicular epithelial cells which is what causes a clogged pore resulting in the clinical picture of acne.

How  long does Retin-A take to work? 
Retin-A is a topical medication that needs to be applied to the skin on a regular basis.  The medication may take two to seven weeks to start improving the appearance of acne.  The medication should be continued after the clearing of the acne because the mechanism of action continues to prevent new acne lesions.

What are the side effects?
The most common side effect is redness and scaling of the skin.  If the medication causes severe irritation the frequency of application may need to be decreased.  Patients should also avoid sun exposure while on the medication due to increased sun sensitivity.

Wolff K, Johnson, RA.  Fitzpatrick’s Color Atlas and Synopsis of Clinical Dermatology. Sixth Edition. 2009.