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Salicylic vs glycolic vs lactic — which acid is actually right for your skin?
Three of the most-used exfoliating acids — and they target completely different problems. Salicylic dives into oily pores. Glycolic resurfaces the entire skin. Lactic exfoliates gently while hydrating. Use the wrong one and you waste 12 weeks on a problem it was never going to fix. Eight questions; we return the right acid, the right strength, frequency, and brand picks at three budget tiers.
The three acids do fundamentally different things because they're chemically different. Salicylic acid (BHA — beta-hydroxy) is oil-soluble, so it dives into oily pores and breaks down sebum and dead cells. Glycolic acid (AHA — alpha-hydroxy) is water-soluble with the smallest molecule of any AHA, so it penetrates fastest and resurfaces the entire skin surface aggressively. Lactic acid (AHA) has a larger molecule that stays more on the surface and includes a hydrating side-effect, making it the gentlest of the three. Mandelic and PHA are even gentler alternatives. Pick wrong and you'll be irritated or under-treated.
Salicylic acid (BHA) — the oil-soluble pore-clearer
The only chemical exfoliant that's oil-soluble, which means it penetrates into the sebum-filled pore rather than just acting on the surface. This makes it uniquely effective for:
- Blackheads and closed comedones
- Whiteheads
- Active acne (especially comedonal)
- Oily skin with congestion
- Body acne, scalp acne, fungal acne (broader BHA category)
Strengths: 0.5% (gentle), 1% (standard daily), 2% (acne strength), 3% leave-on (maximum, irritating), 30% wash-off peel (professional).
Best for: oily, acne-prone, congested skin. Combination skin's oily zones. Anyone whose problem is pore-related (blackheads, congestion).
Tolerance: relatively gentle for an acid. 2-3x weekly to start, daily for most people by week 4-6 if well-tolerated.
Top picks:
- Budget: Stridex Maximum 2% pads ($7), The Inkey List BHA 2% ($10)
- Mid: Paula's Choice 2% BHA Liquid ($35) — the most-recommended salicylic acid product on the internet
- Premium: SkinCeuticals LHA Solution ($90), iS Clinical Active Serum ($142)
Glycolic acid (AHA) — the surface resurfacer
Smallest molecule of any AHA, which means deeper and faster penetration. The most aggressive option of the three commonly-discussed acids:
- Surface texture and roughness
- Fine lines and crepey skin
- Pigmentation and uneven tone
- Dullness and lack of glow
- Aged or sun-damaged skin
Strengths: 5% (daily for some), 7% (typical toner strength), 10% (treatment strength), 30%+ (professional peels only).
Best for: normal-to-resilient skin focused on anti-aging, texture, or pigmentation.
Tolerance: more irritating than salicylic or lactic. 2x weekly to start; max every other night. Causes the most photosensitivity of the three — strict daily SPF non-negotiable.
Caution: not great for sensitive skin, rosacea, or active inflammatory acne. The aggressive surface action can flare both.
Top picks:
- Budget: The Ordinary Glycolic Acid 7% Toning Solution ($10)
- Mid: Paula's Choice 8% AHA Gel Exfoliant ($35), Pixi Glow Tonic 5% ($15-29)
- Premium: SkinCeuticals Glycolic 10 Renew Overnight ($85), Dr. Dennis Gross Alpha Beta Universal Daily Peel ($88 — combination AHA/BHA)
Lactic acid (AHA) — the gentle, hydrating exfoliant
Larger molecule than glycolic — penetrates less aggressively, stays more on the surface. Built-in hydration benefit because lactic acid is a humectant. The friendliest acid for sensitive skin and beginners:
- Mild texture improvement
- Gentle pigmentation fading
- Hydration on dehydrated skin
- Beginners new to acids
- Sensitive skin types
- Dry or aging skin needing exfoliation + moisture
Strengths: 5% (gentle daily), 10% (treatment), 30%+ (professional only).
Best for: dry, sensitive, dehydrated, or beginner skin. People who reacted to glycolic but want some AHA benefit.
Tolerance: gentlest of the three at equivalent strengths. 2-3x weekly to start; many people tolerate daily at 5%.
Top picks:
- Budget: The Ordinary Lactic Acid 5% + HA ($8), The Ordinary Lactic Acid 10% + HA ($8)
- Mid: Sunday Riley Good Genes All-In-One Lactic Acid Treatment ($85 — popular but expensive), Krave Beauty Kale-lalu-yAHA ($25)
- Premium: SkinCeuticals Glycolic 10 Renew Overnight contains some lactic — closest premium option is custom prescription
The honorable mentions
Mandelic acid (AHA)
Even gentler than lactic. Largest molecule of common AHAs. Particularly good for skin of color (less PIH risk) and acne (some antibacterial action). Underrated for sensitive skin.
Top pick: The Ordinary Mandelic Acid 10% + HA ($8) — excellent budget option.
Polyhydroxy acids (PHA: gluconolactone, lactobionic acid)
Even larger molecules than mandelic. Effectively non-irritating. Provide mild exfoliation plus antioxidant and humectant effects. Excellent for severe sensitivity, rosacea, and very dry skin.
Top picks: Neostrata Bionic Face Cream ($43), Stratia Soft Touch ($25).
Azelaic acid
Not an AHA or BHA technically — a dicarboxylic acid. Multi-functional: anti-inflammatory, anti-bacterial, tyrosinase inhibitor for pigmentation. Pregnancy-safe. Excellent for rosacea and PIH in skin of color. Different category than the others on this list but often grouped with them.
Critical layering rules
- Never mix two acids in one routine — pick one. Combination products are exceptions (e.g., Drunk Elephant TLC Sukari Babyfacial combines acids in one formula).
- Never combine with retinol same night — alternate nights or use skin cycling.
- Wait 15 minutes after applying — acids work at low pH (3-4); applying neutral pH products immediately deactivates them.
- Mandatory daily SPF — all AHAs increase UV sensitivity; glycolic and lactic create more photosensitivity than salicylic.
- Pause 5-7 days before significant sun exposure (vacation, beach) — let the skin recover before UV blast.
The ramp-up rule
Standard introduction for any new acid:
- Week 1: patch test on inner forearm. Wait 24 hours, watch for reaction.
- Week 2: 1-2 nights per week. Apply on clean dry skin, wait 15 min, then moisturizer.
- Week 3-4: 2-3 nights per week if tolerated.
- Week 5-8: every other night or daily depending on strength + skin tolerance.
- Indicator to slow down: persistent redness, stinging, peeling, or new sensitivity. Drop frequency or pause.
How long until results
- Week 1-2: skin feels smoother to touch.
- Week 4-6: visible improvement in texture and pore appearance.
- Week 8-12: pigmentation fading, brightness improvements.
- Beyond 12 weeks: continued slow improvement; results plateau at month 4-6 typically.
Common questions
What's the difference between salicylic, glycolic, and lactic acid?
Salicylic acid is a BHA — oil-soluble, so it penetrates into pores and breaks down sebum. Best for acne, blackheads, congestion. Glycolic acid is the smallest AHA molecule — water-soluble, penetrates fastest and most aggressively, resurfaces the skin surface. Best for texture, fine lines, pigmentation. Lactic acid is a larger AHA molecule — gentler, stays more on the surface, has a built-in hydrating effect. Best for sensitive skin, beginners, dehydrated skin. Mandelic and PHA are even gentler alternatives for severely sensitive skin or skin of color.
Can you use salicylic and glycolic acid together?
In one routine, no — pick one. Combination products like Drunk Elephant TLC Sukari Babyfacial or Paula's Choice Skin Perfecting 4% BHA + 1% Glycolic are exceptions designed to balance both. Two separate products layered same night is too aggressive for most skin. If you have multiple concerns (e.g., congestion + texture), alternate nights: BHA Monday/Thursday, glycolic Wednesday/Saturday, recovery on the other nights. Or use skin cycling format.
Which acid is best for sensitive skin?
Mandelic acid 5-10% or PHA (gluconolactone, lactobionic acid) are gentlest. Lactic acid 5% is the next step up. Avoid glycolic acid for severely sensitive skin — too aggressive. Salicylic acid 0.5-1% is moderately tolerated by sensitive skin and useful if your concern is acne. For rosacea, BHA is generally tolerated; AHAs are riskier. Patch test any new acid on inner forearm first, wait 24 hours, watch for delayed reaction. Start at twice-weekly maximum and build up over 4-6 weeks.
How often should I use chemical exfoliants?
Depends on the acid and your skin. Standard starting frequency: 2-3 nights per week. Salicylic 2%: many can use daily after 4-6 weeks ramp-up. Glycolic 7-10%: every other night maximum for most skin. Lactic 5-10%: 3-5 nights per week typically tolerated. Daily AHA exfoliation is rarely needed and often counterproductive — the skin barrier needs recovery time between treatments. If skin starts feeling tight, stinging, or peeling, reduce frequency immediately. Daily SPF is non-negotiable while using any acid.