Summarize:

Stop using any products that contain tretinoin, like Retin-A or Differin, at least a week before your chemical peel. These products can irritate your skin, which could impact the outcome of your peel. For glycolic acid and lactic acid peels, discontinue there products for 3-4 days before and after your peel. For TCA peels, stop using them for 5 days before and 10 days after your peel. Perform a mild exfoliation treatment 24 hours prior to your treatment, using a gentle facial scrub. After washing your skin, apply a pH solution to prepare your skin for the peel. Apply a dab of the chemical peel to your forearm or to the area of skin below your ear at the hairline. Leave the solution on for at least a minute before washing it off. Check the patch test after 24 hours to make sure your skin doesn't react negatively to the peel. If your skin looks normal around the test area, proceed with your chemical peel. If your skin is irritated, red, or tender, lower the concentration of the active ingredient (glycolic, lactic or trichloroacetic acid) in the peel solution and try another test. If you get to the lowest concentration of chemicals and still see a reaction, do not do the chemical peel. If you have any signs of an allergic reaction, like itching or hives, do not use the chemical peel. Apply the peel with a Q-tip using your fingers may make your fingers peel.
Stop using tretinoin-based products for a week. Gently exfoliate your face the day before your peel. Do a spot test before applying your peel.