The ABCs of Acid: AHAs and BHA

Welcome to Week 2 of my Acid 101 series!! Today I’ll be discussing what AHAs and BHA actually are! I’ll be noting what they do, any similarites/differences between the two acid categories, and which one is (potentially) right for different skin issues you might be looking to correct. I’ll start in alphabetical order of course haha!

How my face feels when I don’t exfoliate 😂

Alpha Hydroxy Acids

AHA is an acronym for alpha hydroxy acids. Aha! #badpunsareawesome. WHAT they actually are is a bit above my pay grade (I’m not a chemist), but what you really need to know: they are a group of natural and/or synthetically derived acids that are used in skincare for different topical effects. The main use of AHAs in skincare is for exfoliation, or shedding the top layers of your skin called the Stratum Corneum. Fun fact: did you know your SC can be anywhere between 20 to 30 cell layers deep? The top 2 or 3 layers of the SC are usually shed regularly by the body through a process called desquamation, but sometimes the skin can use a nudge to move the process along faster…. that’s where these bad boys step in to work work work work work!

The AHAs you’ll find used in skincare are:

  • Glycolic acid (derived from sugar cane)
  • Mandelic acid (from almonds)
  • Lactic acid (from sour milk)
  • Malic acid (from apples)
  • Citric acid (from citrus fruits)
  • Tartaric acid (from grapes… specifically wine)

You’ll find the top 3 in use for exfoliation more often than the others. Malic and tartaric acid are gentler; they’re ideal for long term use in smaller doses, such as in a cream. Citric acid is used often in non-exfoliating products as a preservative and pH adjuster, very rarely as a featured exfoliating acid as it can be quite irritating. So why are the other three the most common?

Glycolic acid has the smallest molecule size, so it penetrates the skin faster and can deliver the fastest results. That makes it the most likely to be irritating though, even at lower percentages (pH dependent; there’s a note about that somewhere below…). Glycolic acid has the fastest/best brightening properties out of all the AHAs, so for my chocolate people who do not want significant lightening results… you’ll want to stay away from it. It’s my favorite for brightening though!

Lactic acid has a medium sized molecule size, and as our bodies produce it naturally (it’s a component of your acid mantle; more on that another Friday…) it causes little to no irritaion (pH dependent of course). It has brightening properties too, but it takes a bit longer to work than GA. IMHO it’s a great acid to start with. It has a medium sized molecule size, so it’s not as fast as GA in delivering results, but it’s great for long term use! It can also help mositurize the skin. You’ll see LA in non-exfoliating products for that purpose. It’s probably the most common acid you’ll see in skincare these days (yes, even in drugstore shit LOL). 

Mandelic acid is the newest of the Main 3. It has the largest molecule size out of all the AHAs, meaning that it’s a bit slower to work. It does everything glycolic and lactic does (just reallllyyyy sloowwww), but it’s better suited to those with sensitive skin. That’s what makes it such a great acid however; you can get the same results as GA or LA without the irritation, even at higher concentrations (pH dependent; however compared to a similar pH/concentration of GA or LA it will not be as irritating). I also find it to be the best AHA to use long term; you can use it everyday with no issues. I recommend MA to all my dark skin peeps; it helps even out skin tone and eradicate PIH without the more dramatic overall lightening effects of GA.

AHAs are great for:

  • Reducing fine wrinkles
  • Reducing dryness
  • Preventing/getting rid of acne
  • Reducing Post Inflammatory Hyperpigmentation (PIH)*
  • Evening skin tone*
  • Brightening skin*
  • Reversing sun damage*
  • Lightening mild forms of melasma*

*these require the use of a class of chemicals called tyrosinase inhibitors if you want the best results. They stop an enzyme called (surprise!) tyrosinase from producing excess melanin, which is the root of these starred issues. You CAN just use AHAs, but it will require longer treatment or the use of deeper chemical peels.

Beta Hydroxy Acid

BHA is an acronym for Beta Hydroxy Acid. As far as skincare’s concerned there’s just one BHA: salicylic acid. Salicylic acid can be lab manufactured or derived from willow bark. It’s related to aspirin, so skip it if you’re allergic. BHA is widely known for its (very impressive) acne fighting powers, but did you know it also exfoliates the skin like AHAs? It’s also used to treat a variety of skin conditions such as psoriasis, dandruff, pilaris keratosis (“chicken skin”), and even warts. It has what’s called a keratolytic effect; it breaks down keratin, which is what our skin is made of. It’s also comedolytic; meaning it breaks down whiteheads (comedones), which are caused by a buildup of old skin cells and sebum. The BHA gets in there, dissolves all the yucky shit, and voila! Annoying whiteheads are gone.

BHA is great for:

  • Preventing/getting rid of acne
  • De-clogging pores
  • Exfoliation without brightening properties
  • Reduces excess sebum (oil) production
  • Reducing redness associated with rosacea
  • Antibacterial properties
  • Anti-inflammatory purposes
  • Smoothing out rough skin

Ok, so they kinda do the same shit, you say. WTF is the difference then??

Well, it’s a subtle difference: AHAs are water soluble (they work better in water enviornments) and therefore work best on your skin’s surface. AHAs are better for drier skin types, as they help with more issues while keeping the skin moisturized. They’re better at brightening and anti-aging in the long run as well. BHA is oil soluble (it works better in oily enviornments), and therefore it can get deep into pores to get ’em clean. BHA can be quite drying however. Those distinctions make BHA more effective for oily skin types, since they tend to have deeper skin issues (acne + clogged pores) than an AHA might be able to handle, plus the oil control is a definite plus to that skin type.  

Pretty much all skin types can benefit from having both acid types in their routine though! People with combination skin especially (that’s most of us I reckon) can use a combination of AHA and BHA in the same routine in different parts of the face, while dry skin peeps can alternate days between the two and pile on the hydration on the BHA days. Oily peeps… you can also alternate every other day, or you can use one in the AM and one in the PM. Sensitive skin…? I would stick to mandelic acid, which also has some antibacterial properties but won’t work as well at controlling acne.

Notes on Using Acid in Your Skincare

If you want to get the most benefit from acids, I would suggest rotating between a couple different low percentage acid products in your routine; ideally one AHA and BHA. They work well together to maintain healthy skin activites when used with supporting products in your routine. And with that…Just using acids in your skincare routine isn’t enough to thoroughly resolve the skin issues discussed. In order for you to get optimal results really depends on the type/concentration, specific pH levels, frequency of use, and other supporting ingredients in whatever product you’re using to deliver the acid to your skin…. I’m not going into all of that today however #soon.

If you would like to read more about the individual acids, I highly recommend this well researched post from I didn’t use it as a source, but I thought it was worth a read… I’ve ony touched on the different acids and didn’t even break them all down. Give me a break; I’ve written a fucking novel ovah here already *New York accent*.

I hope you found this helpful. Please let me know if you have any questions about this post, or if you have suggestions for Acid101 leave them below! Hope to see ya for next Friday’s installment! 💜

Souces/Read More:

Book: Milady's Standard Esthetics: Fundamentals; by Joel Gerson


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