Anyone interested in skincare knows that active ingredients are our friends.
Two of the most proven ones are acids and retinoids:
- Acids include alpha-hydroxy acids (such as glycolic and lactic), and beta-hydroxy acids (also known as salicylic acid)
- Retinoids refer to a family of vitamin A derivatives, including over-the-counter retinol as well as prescription-only tretinoin, a.k.a. Retin-A
Both ingredients do everything from resurfacing the skin to fading dark spots to softening wrinkles. So if one active is good, wouldn't a routine with two actives be even BETTER?
Well, not so fast! You may have heard that acids and retinol don't get along well together—and you'd be right. Here are just two of the questions I've received about them lately:
Can chemical exfoliants be used under retinoids? — Nicole
Yep, this is one of the most confusing things in skincare! The good news is you don't have to choose between acids and retinol. It's fine to use both ingredients in one skincare routine. But they should be applied at the right times in order to protect your skin and get the best possible results.
Allow me to explain...
Why Acids and Retinol Don't Mix
Before we get into the "how," I want to briefly touch on the "why"—the reason I'm recommending against applying a retinol right after an acid or vice versa.
Irritation: First of all, there's more risk of irritation when you're using two strong exfoliators at the same time. This can disrupt your skin's barrier and leave you inflamed and sensitive.
Impaired conversion of retinol: Second, retinol doesn't work so well on acidic skin. Remember that it is a weak derivative of vitamin A, and in order for your skin to be able to use it, the retinol must be converted into retinoic acid by the body. This study found that the "hydrolysis reaction is greater at neutral pH," which means the conversion process is more optimal on non-acidic skin.
Inactivation of acid: On the flip side, acids penetrate better at a lower pH (see this study, for example). So if you're layering a retinol with a higher pH over an acid, it might neutralize the acid—bring up its pH—and make it less effective. It's also a waste of good product!
A Quick Word on Retin-A
I don't think you need to worry about impairing the aforementioned conversion process if you're on Retin-A (tretinoin), since it is already retinoic acid.
(Not that I recommend Retin-A anymore, by the way.)
However, I'd still be cautious about layering Retin-A right on top of your acid, since the irritation risk is even greater, and you want to give the acid time to do its job.
Acid and Retinol Routines to Try
Okay, ready to see how you can incorporate both active ingredients into your routine?
Here are some options you can try...
Option 1: Acids Morning, Retinol Evening
The least risky way to use acids and retinoids is to apply them at different times of day.
Does it matter which one you use when? Well, prescription retinoids should always be used at night because they can break down in light and make your skin more sensitive to sunburn. So if you're on Retin-A, you could apply your acid products in the morning.
Over-the-counter retinol doesn't cause the same sun sensitivity, and some of the newer formulations may be photostable enough to wear in the daytime under a good sunscreen. However, most dermatologists still recommend using it at night, with acids in the morning.
Option 2: Alternate Nights
Another option is to only use your active products at night, one active at a time. That could mean:
- Acids one night, retinoids the next
- Two nights of acids, third night retinoids
- Two nights of retinoids, third night acids
- Acids one night, retinoids the next, and then a night off with just moisturizer
Or any other combination, depending on what your skin can tolerate. This is a good way to approach actives if you have sensitive skin, or if you're new to using stronger products and want to gradually build up a tolerance.
Option 3: Wait 30 Minutes
If you do want to go ahead and use an acid and a retinoid at the same time, you can... but only if you've got time to wait in between layers!
It doesn't really matter which one you apply first; just go with the one that has the lightest texture. Typically, this is the acid. For example, I would put on Lotion P50 or The Ordinary Lactic Acid first, because they have a thin consistency.
Then, give it a good 30 minutes. If you can wait an hour, even better! This will allow your skin's pH to return to normal.
Once the waiting time is up, you can apply your second active on top. Usually, this is the retinoid (The Ordinary's is thicker and creamy, for example). There's still a chance it may not convert quite as well as it would without the acid, but the waiting time should help a lot.
I hope this clarifies some of the confusion around acids and retinoids!
I know you want ALL the skin benefits—and trust me, I'm the same way. But in the spirit of protecting your skin barrier and not wasting your money (by weakening or inactivating something), I think it's so important to use these ingredients strategically.
Personally, I've had good results applying my favourite COSRX BHA both morning and night, and this retinol (which is coming out soon!) a few nights a week. On the nights I'm too tired to wait the 30 minutes, I'll either skip the BHA or the retinol.
I'd love to hear what works for you!
Does your routine include acids and retinoids?
What's your favourite way to apply them?