- Topical over-the-counter remedies for acne (salicylic acid) for 2 weeks If you have had any of the above, you may still qualify for the study following a washout period (time for your body to completely eliminate, or get rid of, the medication). The study doctor will evaluate whether there is anything else in your history that may affect your safety in the study or interfere with evaluations. He/she may therefore advise you not to participate.