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How Are AHA, BHA, and PHA Different?

06 Sep 2021

For those who are new to the world of skincare, the word “acids” can seem… frightening. But have no fear! As the skincare pros know, the main groups of acids used in skincare products are formulated in precise, safe-for-skin percentages, and aren’t all harsh like the word connotes. Acids can actually be game changers for one’s daily routine. When it comes to chemical exfoliation, two of the most popular acid groups used to exfoliate the skin are AHAs and BHA. In the new Mandelic Acid + Superfood Unity Exfoliant, AHA and BHA unite — along with a third acid, PHA. So what’s the difference between the three? And what does this trio achieve together? Youth To The People’s Director of Education, Laura Cline, weighs in on the key differences and functions of AHA, BHA, and PHA. After all, at YTTP, the language of skincare is the language of science. Class is in session!


Typically derived from fruits or sugars, alpha hydroxy acids are ultra-hydrating and support the sloughing off of dead cells on the surface of the skin. There are many forms of AHAs, including skincare fan favorites glycolic acid and lactic acid, best known for their potency and hydrating abilities respectively. They pair well together, tag-teaming to minimize pores and retain hydration and moisture—as they do in the Kombucha + 11% AHA Exfoliation Power Toner. The Power Toner uses 8% lactic acid and 3% glycolic acid.

The most mellow AHA is mandelic acid due to its large molecule size. Mandelic acid is known for its gentleness and its ability to help even the skin’s complexion. While the Power Toner packs a punch as a dual-purpose resurfacing toner, simultaneously targeting pigmentation and nourishing the skin’s microbiome, the Mandelic Acid + Superfood Unity Exfoliant is considerably more gentle. “The Power Toner has a much higher percentage of AHAs, so it really is meant to be used only at night, a couple of times a week,” says Cline. “The Unity Exfoliant was really built to be like a daily support system.”


The primary form of BHA is salicylic acid, the superstar ingredient known for targeting breakouts. Salicylic acid is derived from willow and is oil-soluble, whereas AHAs are water-soluble. 

“That’s what allows BHA to go into the pore, because oil likes oil,” Cline explains.

BHA can deeply and instantly penetrate the pores to break down oil, dead skin, and debris. In the Superclay Purify + Clear Power Mask, BHA and red willow bark work synergistically with 2% niacinamide to clarify pores and strengthen the skin’s moisture barrier. In the Mandelic Acid + Superfood Unity Exfoliant, a unique formula of 2% BHA (the highest percentage of BHA you can use in this format) and 3% AHA supercharge one another without the risk of serious irritation. 

“This is the first time we've used a combination of AHAs and a BHA in a leave-on exfoliant treatment, so it was formulated by putting antioxidants, barrier-supporting ingredients, and hydrators in,” says Cline. “Normally when you use 2% BHA, your skin can feel tight, dehydrated, or uncomfortable. We were trying to think of a way where we could be very on-brand with ourselves and how we formulate, and make sure that we're really keeping the skin's barrier healthy and hydrated, and not over-stripping.” 


PHAs are lesser known acids—an ingredient Cline calls “a unicorn.” There are a few forms of PHAs (including galactosen and lactobionic acid), but the PHA used in the Mandelic Acid + Superfood Unity Exfoliant is gluconolactone. According to Cline, PHAs work very similarly to AHAs. 

“It’s considered to be almost like a hybrid. It's a little complicated,” Cline shares. “I would, in simplest terms, classify it as a very, very gentle, very large molecule AHA. It doesn't break down skin in an aggressive way, but it gently exfoliates and it’s safe to use during daytime.”

Most of the time, PHAs are found in topical exfoliating and toning treatments in which they function like AHAs to boost hydration and improve moisture barrier health.

When formulating the Unity Exfoliant, the goal was to create a treatment gentle enough that it could be used every day, with the same level of efficiency as a forceful exfoliation treatment that’s intended to be used weekly. 

“That's why we chose mandelic acid at 3%, the highest percentage [in the formula]. Because it also will help with tone, [we added] the BHA at 2% because it's a very efficacious concentration percentage for a leave-on treatment. And then the PHA at 1% was to help give it this extra added boost that would be really gentle to keep its usage flexible,” says Cline.

“It's a much lower risk of irritation with this type of formula,” Cline adds. “This would be a really excellent way for someone to be introduced to exfoliants if they've never done it, especially maybe somebody younger that's just starting to notice breakouts. Our cell turnover starts slowing down with age, [so] really every age and skin type does need an exfoliant. You just have to find the one that fits your routine and makes your skin feel really comfortable.”

Written by Kaitlyn McNab for Youth To The People

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