Everything You Need to Know Before Using Lactic Acid
The Glossary
Lactic Acid 101
This is a transcript from Episode 143 of Gloss Angeles and the first episode of The Glossary, focused on Lactic Acid. The episode first aired on June 1st, 2021.
Milk. Tomato Juice. Joints. Skincare? All of these contain lactic acid.
Hi Glamgelenos! Welcome to The Glossary: a series of episodes that break down everything you need to know about specific ingredients — like lactic acid — featuring a few of our favorite product recommendations. Let’s dive in.
What is Lactic Acid?
Lactic acid is an alpha hydroxy acid, or an AHA. As a chemical exfoliant, it does a few things: it brightens, it smooths, and it evens out skin texture by loosening the bond between dead cells on the skin. It’s found in things like milk due to the natural fermentation process and is also produced by muscles during exertion when exercising — it can delay the cause of fatigue you may feel when working out. There are synthetic forms of lactic acid that can be used, too.
Lactic acid was first discovered by chemist Carl Wilhelm Scheele in 1780, who was the first person to isolate lactic acid from sour milk. (Fun fact: the latin word “lact” means “milk.” The more you know.) A century later, a french scientist, Frémy, produced lactic acid from fermentation. But even before this, Cleopatra was even allegedly known to take sour donkey milk baths because she felt it “renewed her skin,” although it’s debated whether or not the milk would contain enough lactic acid to do anything.
Lactic acid has a variety of uses: tanning leather, preserving processed cheese and giving it flavor, dying wool and more. But how did it become such an applauded ingredient in skincare?
History of Peels
As we mentioned, civilizations like the Egyptians, Greeks, and Romans were utilizing this method, simply feeling that it helped with their complexions. Then, centuries later, dermatologists started introducing it in their research for skin therapies. However, these peels were way more aggressive than even the most potent peels we have today. Ferdinand Ritter von Hebra, known as a father of topical dermatology, treated freckles and melasma in 1874 using “exfoliative agents in various combinations.”
And get a load of this: according to the article “A History of Peeling” in the publication “Dermatologic Surgery,” things like iodine and lead were used repetitively to lighten freckles. In other cases, lime-based compresses would blister the skin after being applied for four hours. The blisters would then be punctured, starch would be applied, and the resulting scabs would be removed to reveal lighter skin. I’m willing to do A LOT for my skin but I don’t know if I’d be willing to go through all that.
Fast forward to the 1900s and in 1974 it’s reported that lactic acid is effective in treating dry, rough skin. They are noting that alpha hydroxy acids as a whole are helping with things like acne, keratosis, and concerns related to aging like dullness and wrinkles.
What It Does
Okay, so now we know a little bit about the origin of lactic acid and how it works. But what benefits does it have and who is it best for?
The good news is lactic acid is one of the most researched AHAs. We think of it as a little sister to glycolic acid, which is largely considered the most popular AHA. But don’t let that sway you into thinking it’s not powerful.
Lactic acid works in a few ways: it kills bacteria which makes it a suitable option for those with acne, it can thicken and firm the skin at certain concentrations — between 5%-12% -- to help with fine lines and wrinkles, and helps with cell turnover. But one of the main differentiators of lactic acid is that it allows water to bind with skin, so your complexion will also look more plump.
Because lactic acid is a larger molecule than glycolic acid, it doesn’t penetrate as deeply into the skin. What does this mean for you? You’re going to get a more surface-level exfoliation, making it less irritating for sensitive skin. If you’re just getting into the world of chemical exfoliants, lactic acid is a good starting point.
If you’re deciding whether or not to incorporate it into your routine, it’s great for people with dry or sensitive skin or if you want smoother, firmer skin, and especially if you’re trying to get rid of pigmentation from the sun or leftover acne marks. As an alpha hydroxy acid, it doesn’t penetrate as deep into the pore because it’s water-soluable, not oil-soluable like BHAS, but it’s great for anyone experiencing things like flakiness, large pores, discoloration, fine lines, clogged pores and more.
How to Use It
So you’re sold on lactic acid and all it’s benefits. I mean, who wouldn’t be? It’s like the Jennifer Garner of skincare ingredients: it’s the least intimidating AHA, most people not only tolerate it but benefit from having it in their life, and it’s pretty popular, too. So how do you use it properly?
We recommend using this product at night. And at the risk of sounding like a dead smoke alarm constantly chirping, wear at least SPF 30 the morning after. It is an exfoliant, after all, and you don’t want all of lactic acid’s hard work to be thrown out the window because you didn’t apply sunscreen.
We know oftentimes people who don’t consistently use chemical exfoliants can experience “the purge.” And it may keep you from wanting to try great skincare ingredients like AHAs! Frankly, while possible, it’s rare to break out strictly from introducing lactic acid into your routine. But just in case, we subscribe to the Renee Rouleau approach when using a chemical exfoliant at first: 3 nights on, 3 nights off. That way it loosens up the dead skin cells, exfoliates it away, and you’re left with a clean slate. If you do experience a purge, push through. They can last anywhere between 2-6 weeks since it takes around 28 days for skin cells to fully turnover. I know that doesn’t sound fun, but it’s to your benefit. However, if you’re not sure if it’s a purge or a breakout, contact your skincare professional for their expert advice. We’ll also link a blog post by Renee on our website which goes into this more in depth.
Another tip: you can even incorporate a physical scrub once a week to mechanically remove dead skin. Just remember that you shouldn’t use an exfoliant daily.
And lastly, we know everyone has their own preference, but if you don’t wash your face in the morning, consider doing so when you use lactic acid. It will help sweep away those dead skin cells. If you’re using a retinol, we recommend alternating use; basically, don’t use both ingredients in the same day.
So in closing: use it at night, don’t combine it with multiple ingredients (unless the product you’re using is formulated that way), wear sunscreen and don’t exfoliate everyday. When it comes to wear to use it in your routine, it depends on what type of product it is. For serums, use it after your cleanse and if you tone or use an essence. For treatments, use it once a month as a peel.
For sources and our product recommendations, check out this post.