If you’re familiar with anyone in the BHA family it’s likely salicylic acid. Maybe you went to high school together, or met in adulthood when you started that stressful job. You and sal have a relationship at this point—a close one! Sal’s there for you every time a gnarly zit pops up and has no qualms about dissolving itself in your pores to flush it out. Like a child-sized hand small enough to grab an earring you dropped behind the couch, it’s a helpful pal when you need someone to really get in there.

Until recently, sal acid was the only skincare BHA (acetylsalicylic acid, aka aspirin, is an oral BHA)—until its little sister, lipo-hydroxy acid, hit the scene. Cooked up by L’Oréal chemists in the 80s and only really gaining traction now, LHA is a salicylic acid derivative that’s (dare I say?) better. Well, in some instances at least.

First of all, salicylic acid exhibits a way greater capacity for skin penetration—nearly 10 times as much as LHA. While you might think more penetration equals better results, that’s not always the case. Less initial absorption gives LHA what chemists call a “reservoir effect”, meaning more of it stays active on the surface of your skin for longer. (Studies have shown that, four days after application, about 17-percent of LHA stuck around on the top layer of skin compared with about 10-percent of sal acid.) LHA exfoliates, it just does so slower than salicylic, which more closely mimics the way your skin naturally gets rid of dead cells. It also has a pH that matches up exactly with your skin’s—a weakly acidic 5.5, compared with sal’s more strongly acidic 3. It’s a master of the slow-but-steady glow up without a shell shock.

Sal and LHA are both excellent at slipping into your oily pores to treat them from the inside-out. They both exfoliate, and they stimulate collagen production within skin’s deeper layers. They’re both effective at pretty low concentrations (salicylic is usually used in concentrations from 2 to 4-percent, and LHA has shown great results at just 1-percent), so there’s no need to load up. And they both take after aspirin and exhibit anti-inflammatory properties. Reasons to consider LHA would be if you can only tolerate a low percentage of sal acid or are totally new to it, have sensitive skin, or you just want something you can work in every few days. Pregnant folks concerned with salicylic acid absorption might feel more comfortable using LHA because of its low penetration rate. (Though you should always talk to your doctor about using new skincare ingredients while pregnant or nursing.)

But there’s a catch: since LHA is proprietary to L’Oréal, only L’Oréal-owned brands are allowed to use it. So while salicylic acid is abundant in the skincare aisle, products that feature LHA are few and far between. Skinceuticals has a whole LHA range, but it’s pricey. At the drugstore, you can find it in products from La Roche-Posay (specifically in the Effaclar and Pigmentclar lines), L’Oréal (in the Age Perfect line), Vichy (the Proeven and Idéalia lines, plus this intriguing CelluDestock body cream), and Garnier (look, I don’t know who uses Garnier skincare, but it’s in the Skin Active line if anyone wants to report back).

Should you keep hanging out with sal or give his sister a chance? That’s totally up to you, your skin, and your budget—though it wouldn’t be the first time someone fell for their old pal’s sibling. Salicylic acid will forgive you eventually.

—Ali Oshinsky

Photo via ITG