Can I Use Retin-A Every Night?

Retin-A and other retinoids should be applied daily. Night time application is favored, since retin-a can get deactivated by sunlight. If you get irritation from the cream, add a moisturizer every night as well.
 

Retin-A, and its related topical medications called retinoids, are best used on a regular basis.  Some, to enhance tolerability, may use it every other day, but, in general, it is for once daily use to achieve optimal results.  It is not, however, effective as a spot treatment, so regualr use is necessary.  Some retinoids are photostable, meaning they can be used with good efficacy during the daytime, if you need some flexibility in using the medication.  You should check with your dermatologist to see which preparation you currently have.