← Back to Guides

AHAs & BHAs: The Complete Guide to Exfoliating Acids

This guide provides shopping guidance only—not medical, dermatology, diagnosis, or treatment advice. For health concerns, consult a licensed professional.

Understanding Chemical Exfoliation

Chemical exfoliants use acids to dissolve the bonds between dead skin cells, allowing them to shed more easily. Unlike physical scrubs, they don't require rubbing—you apply them and let chemistry do the work.

The two main categories are AHAs (alpha-hydroxy acids) and BHAs (beta-hydroxy acids). Both exfoliate, but they work differently and are suited for different skin concerns.

AHAs: Alpha-Hydroxy Acids

AHAs are water-soluble acids derived from fruits, milk, or sugarcane. They work primarily on the skin's surface, exfoliating the outermost layer of dead cells.

Benefits of AHAs

• Improve skin texture and smoothness
• Reduce the appearance of fine lines
• Even out skin tone
• Help fade sun damage and age spots (see our hyperpigmentation guide)
• Enhance skin radiance and glow
• Help other products absorb better

Types of AHAs

Glycolic Acid

The most common and most studied AHA. Has the smallest molecule size, so it penetrates most effectively. Best for aging, sun damage, and texture. Can be irritating for sensitive skin.

• Concentrations: 5-30% (higher = stronger)
• Best for: Normal to oily skin, anti-aging, dullness

Lactic Acid

Larger molecule than glycolic, so gentler. Also has hydrating properties. Good for beginners and sensitive skin.

• Concentrations: 5-15% typically
• Best for: Sensitive skin, beginners, dry skin (see our dry skin guide)

Mandelic Acid

Even larger molecule—very gentle. Derived from almonds. Good for sensitive skin and those prone to post-inflammatory hyperpigmentation.

• Concentrations: 5-10% typically
• Best for: Sensitive skin, darker skin tones, beginners

Tartaric Acid, Malic Acid, Citric Acid

Less common as standalone acids but often included in blends for enhanced effect.

BHAs: Beta-Hydroxy Acids

BHA is essentially synonymous with salicylic acid in skincare. The key difference from AHAs: BHAs are oil-soluble, meaning they can penetrate into pores.

Benefits of BHAs

• Penetrate and clean out pores
• Reduce blackheads and whiteheads (see our acne-prone skincare guide)
• Help with oily skin and enlarged pores (see our oily skin care guide)
• Anti-inflammatory properties (good for acne)
• Generally less irritating than AHAs at similar strengths

Salicylic Acid

The primary BHA in skincare. Derived from willow bark (or synthesized).

• Concentrations: 0.5-2% for leave-on products
• Best for: Oily skin, acne, blackheads, enlarged pores
• Also used in: Body acne products (see our body acne guide)

AHA vs. BHA: Quick Comparison

PHAs: A Gentler Alternative

Polyhydroxy acids (like gluconolactone and lactobionic acid) are even larger molecules than AHAs. They exfoliate more gently and have hydrating properties. Good for very sensitive skin, rosacea-prone skin, or those who can't tolerate AHAs (see our rosacea-friendly skincare guide).

How to Start Using Acids

For Beginners

1. Start low and slow: Choose a lower concentration (lactic acid 5%, salicylic acid 0.5-1%)
2. Use 1-2 times per week: Give skin time to adjust
3. Apply to clean, dry skin: After cleansing, before other products
4. Wait before layering: Let the acid work for a few minutes
5. Always use sunscreen: AHAs especially increase sun sensitivity
6. Gradually increase: If tolerated, slowly increase frequency or strength

Signs of Over-Exfoliation

If you experience these, cut back or stop:

• Redness and irritation
• Stinging from products that normally don't sting
• Increased sensitivity
• Dryness and flaking
• Breakouts (can happen when barrier is compromised)

See our skin barrier repair guide if you've over-exfoliated.

Product Types

Cleansers

Gentlest option—acid rinses off so contact time is short. Good for maintenance or sensitive skin.

Toners/Essences

Often called "acid toners." Apply with cotton pad or hands after cleansing. Many popular options in this format.

Serums

Concentrated formulas. Can be potent—follow directions carefully.

Peels

Higher concentrations for weekly use. Not for daily use. Start with lower strengths.

Pads

Pre-soaked pads—convenient and portable. Good for travel or gym bag.

Combining Acids with Other Actives

Generally Fine Together

• Hyaluronic acid (not really an acid—it's hydrating)
• Niacinamide (the myth that they can't be combined is outdated)
• Ceramides

Use Carefully or Separate

• Retinol: Both can be irritating; alternate nights or use at different times of day
• Vitamin C: Can work together but may be irritating; some people alternate AM/PM (see our vitamin C guide)
• Benzoyl peroxide: Can be very drying together

Choosing the Right Acid for Your Concerns

For Anti-Aging/Fine Lines

Glycolic acid—most research for anti-aging benefits

For Acne/Blackheads

Salicylic acid—gets into pores where acne starts

For Hyperpigmentation

Glycolic or mandelic acid (mandelic is gentler for darker skin tones)

For Sensitive Skin

Lactic acid, mandelic acid, or PHAs

For Oily Skin

Salicylic acid—also helps control oil

For Dry Skin

Lactic acid—exfoliates while hydrating

Where to Shop

Frequently Asked Questions