"tretinoin increases cell turnover. for those who have an initial purge, where your acne is getting worse, stay patient!!!!! i know how hard it is to look into the mirror. it will get better. i use it every 3rd night and use cetaphil lotion after applying it. my skin is to sensitive to use it daily. i also take an antibiotic every day. it can take up to 12 weeks for a pimple to form; therefore it takes a few months to clear all the pimples up... including the ones that haven&#039;t fully formed yet! be patient!!!!!"