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The Most Effective Percentages of AHAs, BHAs, and PHAs to Look for in Skincare

29 Sep 2021

Decoding a skincare label is often trickier than it looks and that’s especially true when it comes to acids. Sure, the percentages of AHAs, BHAs, and PHAs are typically right on the bottle, but that’s not all you need to know. Mixing and matching acids is best left to the pros to ensure you have an effective but safe formula. That’s exactly why Youth To The People formulated the Mandelic Acid + Superfood Unity Exfoliant—to maximize the efficacy of each ingredient.

“We have tried and tested these acids at different concentrations together to make sure the product is gentle on everyone for frequent and regular usage,” says Quan Tran, YTTP’s Product Development Manager. “Mandelic acid was chosen instead of glycolic acid due to the fact that mandelic acid is more gentle than glycolic, yet still an effective AHA. Kale, spinach, and green tea extracts were incorporated to provide a boost of vitamins and antioxidants to protect against free radicals. Licorice root extract helps to brighten skin and minimize dark spots.”

When it comes to formulating with acids, it's all in the dose—the outcome is impacted by the pH level of the product. The pH in combination with the percentage determines the effectiveness. 

“I can tell you all skincare products with chemical exfoliants—AHAs, BHAs, and PHAs—are formulated at lower pH, no matter the percentage,” Tran says. “The same applies with the Unity Exfoliant; it was formulated at a pH that all three of these acids can function optimally and effectively. However, this product was not formulated with a low pH such as 3.0 which is more likely to cause irritation.”

“On the other hand,” Tran continues, “there's no point formulating products at neutral or higher pH as the acids will already be neutralized and they can't do their jobs.”

Mixing and matching acids can be a challenge since the wrong combinations and percentages can do more harm than good. 

“Formulating something that is really exfoliating to still be gentle can be a tricky process because you want it to really pack a punch, but you don't want it to dry anybody out,” explains Laura Cline, Senior Director of Product Development + Education at YTTP. “When you dry out the skin, you actually create a bigger problem with the building up of dead skin cells, which is ironic, because that's what you're trying to target with something like exfoliating toners.” However, as cosmetic science continues to evolve, the formulas are getting smarter. 

For those times when you’re relying on skincare products with acids and want to experiment at home, it’s important to understand how they work, even when you don’t have a cosmetic chemist in your bathroom. This breakdown will help you learn the basics of each acid, their perks, and how to best use them. 

AHAs, aka alpha hydroxy acids

This category includes glycolic, lactic, malic, tartaric, and citric acids, to name a few of the most common AHAs. 

“There are a lot of different types of AHAs, which can make it a little bit trickier because they aren’t all created equal and you can use them at different percentages,” Cline says.

AHAs are a group of acids that occur naturally in fruits, sugar cane, and milk, plus they can also be created synthetically. In skincare products they’re used as exfoliants; they remove dead skin cells by loosening the top layer of old and dead skin cells by breaking down the gluey substance that keeps the skin cells held together. 

“This encourages the skin to grow more cells, increasing cell turnover,” Tran says. “As a result, they can reduce the appearance of fine lines, dry skin, blemishes, and keratosis pilaris, as well as smooth skin texture.”

Technically, for global compliance, a product can contain a maximum of 10% AHAs, Tran says. But that level is much too concentrated and harsh to use daily, so it can easily trigger irritation and dry out skin.  

“Everyone's skin is different and everyone has different needs and routines,” Tran says. “For example, one may opt for a product with 10% AHAs so they can use it two to four times a week (depending on skin sensitivity). One may opt for a product with less (2-5%) for more regular usage, perhaps daily.”

If you have sensitive skin, the type of AHA is more important to consider than the percentage.  

“Glycolic acid is kind of like your heavy hitter,” Cline says. “Glycolic acid has a teeny tiny little molecule size, so it can get deeper into pores. The smaller the molecule, think about it being even more exfoliating. The larger the molecule, the more gentle it is, but it still works really well and it doesn't make your skin as sensitive. The nice thing about lactic acid is it can be super hydrating and like a delivery system in formulas, but at a low percentage. If you put it at a higher percentage, it will be used as more of a functional chemical exfoliant, so that one is especially flexible.” 

BHAs, aka beta hydroxy acids 

This group of acids also exfoliates the skin. Examples of BHAs include salicylic acid (or related substances, such as salicylate, sodium salicylate, and willow extract), beta hydroxybutanoic acid, tropic acid, and trethocanic acid. 

“BHAs help to reduce the shedding of skin cells inside pores, reducing the chances of blockage, and break down blackheads and whiteheads,” Tran says. “AHAs don't go down deep into pores to perform these tasks like BHAs do.” 

Since BHAs are liquid soluble, they can go deep into your pores, whereas AHAs stay more on the surface of the skin.  

“BHAs actually go in and break down the excess oil and dead skin that causes congestion,” Cline explains. “BHAs really target blackheads and pimples. For that purpose, an optimal percentage is 2%.” Depending on the product, concentrations of BHAs can range between 0.5 and 5 percent.  

“Typically you should look for 1-2% of BHA in skincare products because they are effective at that level and not too high to cause irritation or dryness,” Tran says. 

PHAs, aka polyhydroxy acids 

PHAs are considered the next generation of AHAs. Common examples of PHAs include gluconolactone, galactose, and lactobionic acid. Similar to AHAs, PHAs work to exfoliate the uppermost layers of skin to smooth out skin texture. 

“But unlike AHAs, PHAs have larger molecular sizes, which makes them gentle and wonderful alternatives, especially for those who can’t tolerate regular AHAs,” Tran says. “This includes dry, sensitive, and even eczema and rosacea skin. PHAs work similarly to gently exfoliate, retain moisture, and strengthen skin barrier function.”

Since PHAs are so gentle, they can be used every day. 

“It doesn't cause your skin to be sun sensitive,” Cline says. “It's basically this really giant molecule of an exfoliator.” 

The optimal percentage of a PHA to look for in skincare products can really range. 

“I've seen products that go as high as 10% PHA,” Tran says. “Meanwhile, I've seen a raw material literature for PHA suggesting the percentage use at 0.5 - 5%. It really depends on what else is in the formula and intention for usage frequency.” 

Written by Celia Shatzman for Youth To The People 

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