Lactic Acid vs Salicylic Acid — Which One’s Right for You?
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It’s no secret that the world of skincare acids can be intimidating, even for us beauty editors whose job it is to know this stuff. But when used correctly the results are impressive, so they’re well worth brushing up on.
Skincare acids are chemical exfoliators that work to target specific concerns, such as active acne, acne scars, excess oil production, the appearance of fine lines, sun spots, uneven skin tone and uneven skin texture to name a few. With the right knowledge, they can even help the most fussy of skin types, just like my rosacea-prone complexion.
The key is choosing what chemical exfoliator works best for you individually. We’re focusing on two popular acids: lactic acid and salicylic acid.
Despite sounding fairly similar, they have key differences worth knowing to deliver the best results. Lactic acid is fantastic for me as someone with sensitive, dry skin to effectively exfoliate whilst ensuring no moisture is lost; something not many of the other acids can do. And salicylic acid is ideal for occasional clearing of congestion and keeping any body acne at bay (yes, it can be used as a body wash!) Above all of the countless other skin benefits, these two deliver an unmatched glow — what’s not to love?
To help arm you with all of the knowledge you need, I’ve called in the help of top dermatologists and skin experts to demystify lactic acid and salicylic acid, breaking down the main difference between the two and which skin type they work best for. Trust me, they’re about to up your skincare game.
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What are AHAs and BHAs?
Before diving into the specifics, let’s look into exactly what we mean when we say AHA and BHA. Hydroxy acids are divided into three categories, alpha hydroxy acids (AHAs), beta hydroxy acids (BHAs) and poly hydroxy acids (PHAs). The main differences between them lie in their molecule size, which determines how they interact with the skin.
Today, we’re just focusing on AHAs and BHAs. When comparing the two, the most notable difference is that AHAs have a much smaller molecule size than BHAs, which means they penetrate deeper into the skin. In addition to this, AHAs are water soluble, while BHAs are oil soluble, allowing them to penetrate the skin’s oil glands and remove grime deep into the pores.
For AHAs, you’ll likely have heard of a few different types, including glycolic acid, mandelic acid, citric acid, malic acid, and lactic acid. In this category, we’re discussing the latter, which is a fantastic ingredient for many skin types, even those with fussy, sensitive skin.
BHAs are a little easier to understand because there’s typically just one used in skincare: salicylic acid. It’s worthy of a category of its own though because it’s a mighty ingredient, best used for acne-prone and oily skin.
What is lactic acid?
Lactic acid, an AHA, is a byproduct of the fermentation of dairy (in skincare though, you’ll find it created in a lab) and has a larger molecule than its sister AHA glycolic acid so isn’t as powerful. For that reason, it’s often a go-to for people with slightly more sensitive skin that don’t tolerate glycolic acid well (meaning they experience irritation).
As with all chemical exfoliators, it’s used to, well, exfoliate the skin without the need for abrasive scrubs. Lactic acid works by “breaking down the bonds securing dead skin cells on the very top layer of the skin, revealing fresh, new skin underneath,” says Dr Geeta Yadav, board-certified dermatologist and founder of FACET Dermatology.
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“This helps improve the appearance of fine lines, wrinkles, dark spots, and in some cases, even breakouts, because dead skin on the surface can trap excess sebum and bacteria, causing pimples to form”, she adds.
The NHS backs this up, saying that lactic acid “helps remove dead skin cells and reduce swelling (inflammation). It improves the appearance of acne scars and makes pores look smaller.”
In addition to these benefits, lactic acid also “enhances the skin’s natural moisture barrier and offers some hydration,” explains Akis Ntonos, dermatology nurse practitioner, injectable specialist and co-founder of Aion Aesthetics.
Lactic acid comes in toners, face masks, and serums thanks to its multi-benefits. You’ll often find it combined with ingredients like hyaluronic acid to offer extra hydrating properties.
What skin types should be using lactic acid?
Most skin types can use lactic acid, but those benefiting the most are those with signs of ageing, dry and sensitive skin. “Cellular turnover slows down as we age and we need the boost from lactic acid to help slough off that dead skin,” explains Dr Yadav. Although it’s a great acid for sensitive skin, those with skin conditions like rosacea — where irritation can be an issue — please proceed with caution and introduce any new product slowly.
What is salicylic acid?
Salicylic acid, a BHA, is derived from the bark of certain plants (like willow bark) but, similarly to lactic acid, is mostly made in a lab for skincare purposes, with the NHS saying it “helps stop pores from becoming clogged.”
“Salicylic acid is oil-soluble, so it goes deeper into the skin and penetrates the pores, leading to a deeper exfoliation and a reduction in oil production,” explains Dr Asmi Sanghvi, a board-certified dermatologist at Mount Sinai.
This is why it works so excellently for those with acne and oily skin because it gets deep enough to slough away dead skin and prevent clogged pores, and thus, breakouts.
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Salicylic acid is found in various skincare products like toners and moisturisers, but it’s particularly great when used in a cleanser. If you’re prone to sensitivity, I love the “short contact therapy” method, which is as simple as it sounds: you allow the product to work for just a few minutes before washing away.
This gives enough time for those ingredients to get hard to work without leaving the product on for too long and risking unnecessary irritation. You’ll also find salicylic acid in lots of targeted spot treatments, which works exceptionally well for busting breakouts.
What skin types should be using it?
“Salicylic acid also aids in controlling excess oil production and has anti-inflammatory properties that can calm redness and inflammation associated with acne,” explains Ntonos.
“It might not be as suitable for dry or sensitive skin types, as it can be drying and potentially irritating if used in high concentrations or excessively,” he adds. That’s why it’s always important to slowly introduce any new skincare product, especially active ingredients like salicylic acid. The last thing you want is to cause an unhappy skin barrier!
Even if you have dry facial skin, you can still benefit from salicylic acid as a body treatment. Body wash containing salicylic acid treats body breakouts and keratosis pilaris — often referred to as chicken skin due to its bumpy appearance — by targeting acne-causing bacteria and reducing inflammation.
Another thing to note with salicylic acid is that it isn’t suitable for those with an aspirin allergy as it belongs in the same family.
How do you know whether lactic acid or salicylic acid is right for your skin type?
OK, so we know what each acid is, but how do you know which to use? In simplified terms, it all comes down to what skin type you have and what you’re trying to achieve.
For dry, sensitive or mature skin
If you’re in these categories and want to maintain exfoliation, keep your skin tone and texture even and generally have a fabulous glow then lactic acid is for you.
For dry and sensitive skin, you’ll probably want to add in lots of extra moisturising ingredients like glycerin, hyaluronic acid and urea. It’s also a good idea to start slowly with a new product, using it once or twice a week and building up as needed.
For acne-prone, oily or combination skin
For more oily skin types, it’s likely you’re looking to either prevent breakouts from occurring, or minimise the breakouts you have, plus control excess oil production.
Salicylic acid does a great job thanks to its ability to penetrate deep into the pores. Start using your chosen product just once a week and increasing this and potentially using a higher concentration as your skin tolerates it.
Now, skin conditions, you’re a little more complicated. For rosacea, eczema, dermatitis (and others), you are likely going to want to avoid acids for the most part.
This is because with skin conditions, the skin barrier is compromised — meaning it’s letting good stuff out and bad stuff in — and acids can sometimes make matters worse. Your best bet is getting individual help from a skincare specialist who can guide you through which acid (and in which form) is best, plus how to introduce it into your skincare routine to give you maximum benefits and minimise risk of flare-ups.
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Can you use both?
In short: absolutely! In fact, if used correctly, the two work in synergy together really well; targeting different layers of the skin. That’s why some brands formulate products containing both ingredients for maximum results. Having said that, you’ve got to make sure it’s right for your skin type (as discussed above) and you’re not over-doing it.
Dry and sensitive skin types might find using both to be a little too irritating and drying.
Should you use lactic acid or salicylic acid first?
As to which you should use first, it really boils down to the products you’ve got. If you’ve got a serum that contains both ingredients, there’s your answer.
However, for separate products, you might have to be a little more thoughtful with your application. You might find that a salicylic acid cleanser works great to target face and body breakouts, followed by a lactic acid serum that has hydrating benefits.
Or, you might prefer to use a lactic acid toner and then pop on a salicylic acid spot treatment to target any pesky pimples. This is where trial and error comes into play; figuring out what works well for you and your skin type.
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The takeaway
Lactic acid and salicylic acid have two very different roles. Sure, they both do an excellent job exfoliating, but they target different layers of the skin and achieve slightly different outcomes.
Lactic acid is great for dry, sensitive and mature skin types looking for cell turnover and a brighter complexion. Whereas, salicylic acid works brilliantly for oily and acne-prone skin to clear breakouts and control excess oil production.
You can use them both together but sensitive skin types should proceed with caution. Glowing skin… here we come.
Meet the experts
Dr Geeta Yadav is a world-renowned board-certified dermatologist and the founder of FACET Dermatology in Toronto, Canada.
Dr Asmi Sanghvi is a board-certified dermatologist at Mount Sinai Health System with a passion for skin, beauty, and integrative wellness. She is currently the only dermatologist & ayurvedic nutritionist Merging East-West to heal your skin and unlock your beauty potential.
Akis Ntonos, FNP-C, is a Dermatology Nurse Practitioner and Injectable Specialist, (a.k.a. Facial Architect) and co-founder of Aion Aesthetics, New York’s premier injectables clinic.
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