The issue is that when you use tretinoin alongside other exfoliating acids, you end up stacking acids that can all disrupt the skin barrier, says Dr. Russak, who adds that it’s worth distinguishing glycolic and lactic acid from salicylic acid as they don’t behave the same way. AHAs, like glycolic and lactic acid, work on the surface, exfoliating the outer layers of the skin.
Using AHAs and tretinoin at the same time “can increase dryness, peeling, redness, and irritation,” says Dr. Gohara. “While removing surface cells can theoretically influence penetration, from a practical standpoint the bigger consideration is tolerability. You want tretinoin to work effectively without unnecessarily irritating the skin.” If you want to use both, and your skin can tolerate them, dermatologists recommend using them on alternate nights.
BHAs, like salicylic acid, are oil soluble and work “especially well inside oily pores, while tretinoin normalizes cell turnover and helps prevent pores from being clogged in the first place,” says Dr. Gohara. “They can complement each other, particularly for acne-prone skin, but using both at the same time may increase irritation without necessarily giving you better results.” Again, the advice is to use them on different days or different times of the day, like a salicylic acid-based cleanser in the morning and tretinoin at night.
When it comes to azelaic acid and tretinoin, “too much of a good thing isn’t always a good thing,” says Dr. Russak. Those with sensitive skin should proceed with caution when using the two ingredients together, as the combination may be too much for their skin to tolerate. As always, it’s important to see how your skin responds to the combination before going all in. “Make sure the barrier isn’t compromised, because if it is, it will be too irritating for the skin,” she adds.
Don’t be surprised if your skin needs time to acclimate to the combination. “When used together, especially at the start of treatment, some people may experience dryness, peeling, redness, stinging, or a temporary increase in skin sensitivity,” says Dr. Yang. Because tretinoin tends to be the more irritating of the two ingredients, these reactions may be particularly noticeable as your skin adjusts to the retinoid.
How should you incorporate tretinoin and azelaic acid into your skin-care routine?
If this is your first time using either ingredient, Dr. Wu recommends starting with azelaic acid before introducing tretinoin if you have sensitive skin, since it’s generally much gentler. For some people, she says, it can take up to a month for the skin to adjust to azelaic acid. And while many can tolerate using it daily from the start, those with sensitive skin should begin every other day, then increase to daily use after a week if they don’t experience irritation.
Alternatively, if your goal is to address comedones or clogged pores, Dr. Wu recommends starting with tretinoin first. She suggests applying it on Monday and Friday nights, initially; if you aren’t experiencing irritation, add a third night, such as Wednesday, before gradually working up to nightly use. “If on a stable routine of tretinoin with no irritation after two weeks,” she says, “you could add azelaic acid. If you can’t go past three nights a week, you can alternate azelaic acid in between. If you’re already using tretinoin nightly, then add azelaic acid during the day.”
