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All the Different AHAs in Skincare + When to Use Them

16 Aug 2021

First comes the cleanser. Then comes the addition of the seemingly non-essential, but absolutely game-changing targeted treatments to stimulate collagen, speed up cell turnover, and bring back glow to lackluster skin. And no formula delivers such results better than those containing alpha-hydroxy acids, (more commonly referred to simply as AHAs). 

“Everyone can benefit from the use of AHAs in their routine, particularly if they notice any dullness in their skin,” says Youth To The People’s Director of Education, Laura Cline, adding that as a group “AHAs are both prevention and cure, and are incredibly hydrating in nature, which allows them to be used more often and at higher percentages than some other active ingredients, like retinol.”

But not all AHAs are created equal, and not every ingredient ending with the word “acid” falls under their gentle, yet powerful umbrella. For example, salicylic acid, which is typically used in spot treatments for blemish-prone skin, is a beta-hydroxy acid (aka BHA), and hyaluronic acid is a humectant.  

“The primary chemical difference between AHAs and BHAs is that AHAs come in a variety of forms and are water soluble, breaking off the glue of dead cells on the skin’s surface, and BHAs are oil-soluble, which allows them to penetrate into the pore and dissolve congestion,” says Cline. “Hyaluronic acid draws water into the skin and is neither an AHA or a BHA.”

Here, Cline opens up her definitive guide to AHAsfrom how to choose the most effective one for you to how to layer them into a routine. 

Glycolic Acid

Derived from sugar cane, glycolic acid is the most common form of AHA found in skincareand it’s the most potent, too. 

“Its primary purpose is exfoliation, and because it has the smallest molecular weight of all the AHAs, it can penetrate the deepest, which is why you’ll typically find it in lower percentages,” says Cline. Like all AHAs, glycolic can cause increased sensitivity, so introduce it every couple of nights if you’re new to the categoryand always be sure to use SPF in the morning. 

Lactic Acid

Lactic acid is another common AHA, often made from corn sugar. 

“It’s more gentle than glycolic, but pairs well with itlike in YTTP’s Kombucha + 11% AHA Exfoliation Power Toner,” says Cline. Where glycolic acid shines as an exfoliant, lactic acid shines as a hydrator, stimulating collagen production and smoothing skin texture. If your skin feels slightly ‘tacky’ after using lactic acid, that’s perfectly normal, and will dissipate soon after moisturizing. 

Mandelic Acid

Containing the largest molecules, mandelic acid is the mildest AHA, and is usually derived from bitter almonds. 

“Mandelic acid is super gentle, hydrating, and helps with cell turnover, making it a great choice for sensitive skin,” says Cline. “That being said, it’s not black and white as it all comes down to the pH and percentage concentration in any given formula. Listen to your skin, and if you’re not sure what it’s telling you, give it a moment to adjust.”

Malic Acid

Malic acidcoming in various forms thanks to its presence in a number of fruits and seedserrs toward glycolic in potency, says Cline, making it a cautionary ingredient for those with sensitive skin. Unlike its fellow AHA counterparts, malic acid has also been shown to be an irritant in clinical studies, which means it’s rarely used in skincare. 

Citric Acid

The least talked about AHA is arguably the most common one. Citric acid is in all types of products to increase stability and maintain a balanced pH level. It’s usually sourced from citrus fruit or juice. 

“We use citric acid in a lot of our formulas at YTTP, but not as an exfoliant ingredient,” says Cline. “Its presence allows other AHAs, like glycolic and lactic acid, to penetrate more effectively and be used at higher percentages.” The multi-tasking acid has also been proven to increase the rate of cell renewal and help fade hyperpigmentation from sun damage. 

Written by Elsa de Berker for Youth To The People

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