AHA vs. BHA vs. PHA: Which Exfoliating Acid Is Best for Your Skin?

Chemical exfoliation is one of the most effective ways to achieve smooth, radiant, and clear skin. But with so many acids on the market—AHA, BHA, PHA, and even LHA—it’s easy to feel overwhelmed. Each type works differently, targets different skin concerns, and suits different skin types. In this comprehensive guide, we’ll break down the differences between AHA, BHA, and PHA, help you choose the right exfoliating acid for your skin, and show you how to incorporate them into your routine safely.

What Are Exfoliating Acids?

Exfoliating acids are chemical compounds that dissolve dead skin cells, unclog pores, and promote cell turnover. Unlike physical scrubs that can cause micro-tears, chemical exfoliants work gently on the skin’s surface or inside the pores. They are categorized by their molecular size, solubility (water vs. oil), and depth of action.

The three most popular types—AHA, BHA, and PHA—are all hydroxy acids, but they differ in their chemical structure and how they interact with your skin. Understanding these differences is key to choosing the right product for your specific needs.

AHA (Alpha Hydroxy Acids) – The Surface-Level Exfoliator

What it does: AHAs are water-soluble acids that work on the skin’s surface. They dissolve the bonds between dead skin cells, revealing fresher, brighter skin underneath. Common AHAs include glycolic acid, lactic acid, and mandelic acid.

Best for: Dullness, uneven texture, fine lines, hyperpigmentation, and dry or sun-damaged skin. AHAs are excellent for improving skin tone and radiance.

Skin type suitability: Normal, dry, and aging skin types. Those with sensitive skin should start with a lower concentration (e.g., 5% lactic acid) and work their way up.

How to use: Apply a leave-on AHA toner or serum at night, 2-3 times per week. Always follow with sunscreen in the morning, as AHAs increase sun sensitivity. For a more intensive treatment, consider an in-office peel or a high-strength at-home peel like The AHA BHA PHA LHA 35 Peel, which combines multiple acids for a professional-level glow.

Popular AHA Products from COSRX

For those new to AHAs, the AHA 7 Whitehead Power Liquid is a gentle yet effective option. It contains 7% glycolic acid to smooth skin texture and reduce whiteheads without irritation. If you prefer a toner that also cleanses, the Low pH Niacinamide Micellar Cleansing Water is a non-stripping micellar water that preps your skin for exfoliation without disrupting your barrier.

BHA (Beta Hydroxy Acid) – The Pore-Penetrating Exfoliator

What it does: BHAs are oil-soluble acids that can penetrate deep into the pores. The most common BHA is salicylic acid, which is derived from willow bark. BHAs exfoliate inside the pore lining, helping to dissolve sebum and debris that cause blackheads and whiteheads.

Best for: Oily, acne-prone, and combination skin. BHA is ideal for treating blackheads, whiteheads, clogged pores, and mild acne. It also has anti-inflammatory properties, making it useful for red, inflamed breakouts.

Skin type suitability: Oily, combination, and acne-prone skin. Sensitive skin may tolerate BHA better than AHA because it is less irritating at lower concentrations.

How to use: Apply a BHA toner or serum to clean, dry skin. Start with 1-2 times per week, then gradually increase to every other night if your skin tolerates it. Because BHA is oil-soluble, it works well for those with excess sebum production.

PHA (Poly Hydroxy Acids) – The Gentle Giant

What it does: PHAs are larger molecules than AHAs, so they don’t penetrate as deeply. They work on the skin’s surface, providing gentle exfoliation while also attracting moisture. Common PHAs include gluconolactone and lactobionic acid.

Best for: Sensitive skin, rosacea, eczema, and first-time exfoliation users. PHAs are also great for those with dehydrated skin because they offer humectant properties.

Skin type suitability: All skin types, especially sensitive, reactive, and dry skin. PHAs are the most gentle of all exfoliating acids.

How to use: PHAs can be used daily or every other day, depending on your skin’s tolerance. They are safe to combine with other active ingredients like niacinamide or peptides. For a soothing exfoliation, look for a PHA toner or mask.

If you’re looking for a multi-tasking product that combines exfoliation with deep hydration, consider a hydrogel mask. The COSRX The Peptide Collagen Lifting Glow Hydrogel Mask doesn’t exfoliate directly, but it works beautifully after a PHA treatment to plump and brighten your skin without irritation.

AHA vs. BHA vs. PHA: Quick Comparison Table

Feature	AHA	BHA	PHA
Solubility	Water-soluble	Oil-soluble	Water-soluble
Depth of action	Skin surface	Inside pores	Skin surface (gentle)
Best for	Brightening, texture, anti-aging	Acne, blackheads, oily skin	Sensitive, dehydrated skin
Irritation potential	Moderate to high	Moderate	Very low
Sun sensitivity	Yes	Yes (mild)	Minimal
Frequency	2-3x/week	1-3x/week	Daily to every other day

How to Choose the Right Exfoliating Acid for Your Skin

1. Identify Your Primary Skin Concern

• Dullness, uneven skin tone, or fine lines: Go with an AHA (e.g., glycolic or lactic acid).
• Clogged pores, blackheads, or acne: Choose a BHA (salicylic acid).
• Sensitive or reactive skin: Opt for a PHA.
• Combination concerns: You can alternate between AHA and BHA on different nights, or use a product that combines them.

2. Consider Your Skin Sensitivity

If you have a compromised skin barrier or are prone to redness, start with PHA. It’s the safest option for building tolerance. Once your skin adapts, you can introduce a low-concentration AHA or BHA.

3. Look for Multi-Acid Blends

Advanced users can benefit from products that combine multiple acids. For example, The AHA BHA PHA LHA 35 Peel is a powerful exfoliating treatment that targets multiple concerns at once. It’s ideal for weekly use when you want a deep, professional-level resurfacing.

How to Layer Exfoliating Acids Safely

Layering acids can be tricky. Here are some golden rules:

• Don’t mix strong acids in the same routine. For example, don’t use a high-concentration AHA toner followed by a BHA serum. Instead, alternate nights.
• Use pH-dependent products correctly. Most exfoliating acids work best at a low pH (3.0–4.5). Apply them to clean, dry skin and wait 10–15 minutes before layering other products.
• Always follow with hydration and sunscreen. Exfoliation increases cell turnover, making your skin more vulnerable to UV damage. Sunscreen is non-negotiable.
• Start slow. Begin with once a week, then increase frequency as your skin builds tolerance.

Common Mistakes to Avoid

1. Over-exfoliating: Using acids too often can strip your skin barrier, leading to redness, peeling, and breakouts. Listen to your skin—if it feels tight or stings, take a break.
2. Skipping sunscreen: AHAs and BHAs increase photosensitivity. Without SPF, you risk hyperpigmentation and premature aging.
3. Using acids with other strong actives: Avoid using AHA/BHA with retinoids, benzoyl peroxide, or high-concentration vitamin C in the same routine. Alternate days instead.
4. Neglecting hydration: Exfoliating acids can be drying. Follow up with a hydrating toner, serum, or moisturizer to maintain your barrier.

When Should You See Results?

Results vary depending on the acid and your skin’s turnover cycle. Typically:

• AHA: You may notice smoother texture and brighter skin within 2–4 weeks.
• BHA: Blackheads and clogged pores may start to clear in 4–6 weeks.
• PHA: Gentle improvements in texture and hydration can be seen in 4–8 weeks.

Consistency is key. Stick with a routine for at least 8 weeks before evaluating results.

Final Thoughts: Which Acid Is Best for You?

There’s no one-size-fits-all answer. The best exfoliating acid depends on your skin type, concerns, and tolerance. For most people, a balanced routine includes a gentle PHA for daily maintenance and a stronger AHA or BHA for targeted treatment 1-3 times per week.

Remember, exfoliation is a marathon, not a sprint. Start low, go slow, and always prioritize your skin barrier. If you’re ready to elevate your exfoliation game, explore our range of exfoliating acids and treatments designed for every skin type.

Ready to find your perfect exfoliant? Discover the power of The AHA BHA PHA LHA 35 Peel for a deep, transformative resurfacing experience that combines the best of all worlds.