More susceptible to getting burned
Tretinoin is a retinoid and it can make you more susceptible
to getting burned with prolonged sun exposure. Sunlight can also make tretinoin
less effective. If you are using tretinoin I would recommend practicing good
sun protection and using it as directed.
Sunlight and Retin A
You do not need to completely stay away form any light while using Tretinoin. The reason dermatologists warn their patients to avoid sun exposure, is that the sun breaks down the Tretinoin molecule rendering it ineffective. Adapelene, a synthetic Retinoid does not have this characteristic and is only mildly broken down by sun exposure. For this reason it can be used in the sun.
It is true that your face might turn a bit more red with Retin A on it, but such redness is usually minor and comes from the combined effect of the thinning of the cornified layer of the skin and perhaps, the fact that Retinoids can have a mild phototoxic effect.