AHAs vs. BHAs: A Complete Guide to Chemical Exfoliants
AHAs and BHAs both exfoliate, but they target different concerns. Learn how glycolic, lactic, and salicylic acid work, which suits your skin, and how to use them safely.
Chemical exfoliants can transform dull, rough, or congested skin, often more gently than scrubs. The two most common types are alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs). They both remove dead skin cells, but they work differently and suit different skin concerns.
Here's how to tell them apart and choose the right one for you.
What Is Chemical Exfoliation?
Your skin naturally sheds dead cells, but this process slows with age, sun damage, and certain skin conditions. When dead cells build up, skin can look dull, feel rough, and develop clogged pores.
Chemical exfoliants loosen the bonds between dead skin cells so they can shed more easily. Unlike physical scrubs, they don't rely on friction, which can make them gentler when used correctly.
Alpha Hydroxy Acids (AHAs)
AHAs are water-soluble acids, often derived from fruit, milk, or sugar. They work mainly on the skin's surface.
Common AHAs
| AHA | Source | Characteristics |
|---|---|---|
| Glycolic acid | Sugarcane | Smallest molecule; most potent; can be irritating |
| Lactic acid | Milk | Gentler; also hydrating |
| Mandelic acid | Bitter almonds | Large molecule; gentle; good for sensitive skin |
| Citric and malic acids | Fruits | Often used in combination formulas |
Best For
- Dull, uneven skin tone
- Rough texture
- Fine lines
- Dry or sun-damaged skin
- Hyperpigmentation
Beta Hydroxy Acids (BHAs)
The main BHA in skincare is salicylic acid. Because it's oil-soluble, it can penetrate into pores and dissolve the mix of oil and dead skin that causes clogs.
Best For
- Oily skin
- Blackheads and whiteheads
- Acne-prone skin
- Enlarged-looking pores
Salicylic acid also has anti-inflammatory properties, which can help calm red breakouts.
AHA vs. BHA at a Glance
| Feature | AHA | BHA |
|---|---|---|
| Solubility | Water | Oil |
| Works on | Skin surface | Surface and inside pores |
| Best for | Dryness, dullness, texture, sun damage | Oiliness, clogged pores, acne |
| Skin types | Normal to dry | Oily to combination |
Polyhydroxy Acids (PHAs): A Gentle Alternative
PHAs, like gluconolactone and lactobionic acid, are larger molecules that exfoliate gently and also hydrate. They're a good option for sensitive skin or for people who find AHAs too irritating.
How to Choose
- Dry or sun-damaged skin: Start with lactic acid.
- Normal skin with dullness: Try glycolic acid at a low concentration.
- Oily or acne-prone skin: Use salicylic acid.
- Sensitive skin: Try mandelic acid or a PHA.
- Combination skin: You might use BHA on your T-zone and AHA on your cheeks.
How to Use Chemical Exfoliants Safely
- Start slowly. Use your exfoliant two to three times a week at first.
- Apply at night. AHAs can increase sun sensitivity.
- Apply to clean, dry skin.
- Follow with moisturizer.
- Wear sunscreen every morning. The FDA notes that AHAs can increase sun sensitivity, so daily sunscreen is essential.
Pro tip: Leave-on exfoliants such as toners and serums tend to be more effective than rinse-off cleansers, which only stay on your skin briefly. If you're new to acids, though, a cleanser can be a gentler way to start.
Signs You're Over-Exfoliating
Too much exfoliation can damage your skin barrier. Watch for:
- Redness or stinging
- A tight, shiny, or "plastic" look
- Increased sensitivity to products
- New breakouts or flaking
If this happens, stop all exfoliants and focus on gentle cleansing and moisturizing for one to two weeks.
Can You Use AHAs and BHAs Together?
Yes, many products combine them. You can also alternate nights or apply them to different areas. Avoid using them on the same night as a retinoid if your skin is sensitive.
Ingredients to Use With Caution
- Retinoids: Alternate nights to reduce irritation.
- Vitamin C (L-ascorbic acid): Some people find layering it with acids irritating. Try vitamin C in the morning and acids at night.
- Physical scrubs: Don't combine with chemical exfoliants.
Frequently Asked Questions
Can I use AHAs or BHAs every day?
Some people can tolerate daily use of gentle formulas, but most do best with two to four times a week.
Are chemical exfoliants safe during pregnancy?
Many dermatologists consider glycolic and lactic acid acceptable during pregnancy, while high-strength salicylic acid is often avoided. Always check with your doctor.
Do chemical exfoliants help with acne scars?
They can help fade dark marks over time. Deeper textural scars usually need professional treatment.
The Bottom Line
AHAs are best for surface concerns like dullness, texture, and dryness. BHAs are best for oily, acne-prone skin and clogged pores. Start slowly, use moisturizer, and always wear sunscreen. With the right exfoliant, you can enjoy smoother, brighter skin.
Medical disclaimer: This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a board-certified dermatologist or qualified healthcare provider about your skin. Read our full disclaimer.
