This post was reviewed and updated by Sarah Otto, Dermatology Nurse Practitioner and Founder of Otto Skin Goods on July 8, 2026.
Exfoliating acids in skincare have gained popularity over the past few years, and for good reason! Acids are multifunctional, because they’ve been shown to improve mild acne, fade hyperpigmentation, boost collagen production, smooth fine lines and accelerate your cell turnover rate to promote a brighter, more refreshed appearance.
So, what are acids, anyway?
Acids are a skincare ingredient used to exfoliate. They work by loosening the fluid that binds the cells to the upper surface of your skin. This leads to increased shedding of the upper layers of your complexion, leading to a smoother, brighter tone.
Let’s Talk About Alpha Hydroxy Acids (AHAs)
Of all the different acids on the market today, alpha hydroxy acids (AHAs) are the most effective—and the most irritating. AHAs are water-soluble and work mainly on the outermost layer of the skin. The top AHAs include Glycolic Acid, Lactic Acid, Mandelic Acid and Fruit Acids, also referred to as Multifruit AHAs. Let’s take a closer look at a few of these…
Glycolic Acid
- Derived from sugar
- Smallest molecule of all the acids
- Penetrates the deepest and works the best
- Increased risk of irritation and sun sensitivity
- Regenerates collagen production
- Evens skin tone and texture
- Smooths fine lines and wrinkles
Lactic Acid
- Derived from sugar or fermented milk
- Second smallest molecule
- Gentler than glycolic, which makes it a moisturizing agent, too
- Good for those with sensitive skin
- Smooths and evens rough skin
Fruit Acids
- The gentlest option
- Citric-derived from lemon or grapefruit, and malic from apples
- Largest molecule
- Works mainly on the uppermost layer of the skin
- Gentle enough for daily use
- Star ingredient in The Multitasker Night Serum 1(5% Multifruit AHA)
- May be combined with stronger acids, such as glycolic or lactic
- Used once or twice a week
Let’s Talk About Beta Hydroxy Acids (BHAs)
BHAs, aka beta-hydroxy acids, are considered oil-soluble, which means they penetrate deeper into the pores, allowing them to work better for oily, acne-prone skin. They also have anti-bacterial and anti-inflammatory properties which help to dissolve excess oil in the pores. So, as you can imagine, BHAs are great for those who suffer from mild acne, clogged pores, white heads and blackheads.
The most common BHA is Salicylic Acid—which is best known for its success in treating acne. It penetrates and dissolves oil-clogged pores, exfoliates dead cells and also has anti-inflammatory properties!
Skincare Acid Safety & Frequency of Use
The two main concerns of overusing AHAs is increased sun sensitivity and irritation. Over time, these can cause damage to the skin barrier. BHAs are typically reserved for less frequent use or only for those treating acne.
If you’re using AHAs for skin rejuvenation, evening skin texture and preventing mild breakouts, it’s best to use a gentler AHA, such as fruit acids, on a daily basis. From there, you’ll want to add a stronger combination of glycolic, lactic and salicylic acid one to three times a week, depending on your tolerance.
The bottom line? Acids work quickly and efficiently to achieve healthy, glowing skin—which can be addictive. Unfortunately, overuse can result in the opposite effect. Acids have a meaningful place in your skincare routine, but you need to know how and when and which type of acid to use.
Need a hand? Here’s an example of what my nighttime skincare routine looks like:
Step One: Wash with Otto’s gentle hydrating cleanser, The Good Day Face Cleanser (2% ceramides).
Step Two: Swipe on a few pumps of Otto’s fruit acid and niacinamide serum, The Multitasker Night Serum (15% multifruit AHA + 7% niacinamide).
Step Three: End by smoothing on Otto’s vitamin C face oil, The Fresh Start Face Oil (20% tetrahexyldecyl ascorbate).
Step Four: Use a stronger glycolic, lactic or salicylic acid product one to three times a week, or as needed.
Frequently Asked Questions
What are exfoliating acids and how do they work?
Acids are skincare ingredients that exfoliate by loosening the substance that binds dead skin cells to the surface of your skin. This encourages increased shedding of the upper layers, revealing a smoother, brighter complexion underneath.
What's the difference between AHAs and BHAs?
AHAs (alpha hydroxy acids) are water-soluble and work mainly on the skin's outer layer, making them ideal for texture, tone, and signs of aging. BHAs (beta hydroxy acids) are oil-soluble, so they penetrate deeper into pores, making them better suited for oily or acne-prone skin.
What are the main types of AHAs?
The top AHAs are Glycolic Acid, Lactic Acid, and Fruit Acids (also called Multifruit AHAs). Each varies in molecule size and strength, with glycolic being the smallest and most potent, and fruit acids being the largest and gentlest.
Is Glycolic Acid good for beginners?
Not necessarily. Glycolic Acid has the smallest molecule size, so it penetrates the deepest and works the most effectively, but it also carries a higher risk of irritation and sun sensitivity. It may be better suited for those who've already built up some tolerance to acids.
What skin type is Lactic Acid best for?
Lactic Acid is gentler than glycolic acid and doubles as a moisturizing agent, making it a good option for those with sensitive skin who still want to smooth and even out rough texture.
What are Fruit Acids, and who should use them?
Fruit Acids (derived from sources like lemon, grapefruit, or apple) have the largest molecule size, making them the gentlest AHA option. They work on the skin's uppermost layer and are gentle enough for daily use, though they can also be paired with stronger acids like glycolic or lactic for added benefits.
What is the most common BHA, and what does it do?
Salicylic Acid is the most widely used BHA. It's especially effective for acne because it penetrates and dissolves oil-clogged pores, exfoliates dead skin cells, and has anti-inflammatory properties.
How often should I use exfoliating acids?
It depends on the acid type and your skin's tolerance. Gentler AHAs, like fruit acids, can typically be used daily. Stronger acids, such as glycolic, lactic, or salicylic, are generally recommended one to three times a week. BHAs are usually reserved for less frequent use or specifically for acne treatment.
What happens if I overuse exfoliating acids?
Overuse of AHAs can increase sun sensitivity and skin irritation, which over time may damage the skin barrier. While acids can deliver fast results, more isn't always better; balance and consistency matter more than frequency.
How can I incorporate acids into my nighttime routine?
A simple approach: start with a gentle cleanser, follow with a fruit acid serum, and finish with a nourishing face oil. Stronger acids (glycolic, lactic, or salicylic) can then be layered in one to three times a week, depending on your skin's tolerance.
