AHA vs BHA vs PHA: Complete Exfoliation Guide for Indian Skin

AHA (Alpha Hydroxy Acids): surface resurfacing for texture, tone, and fine lines

AHAs are water-soluble acids that work on the skin surface (stratum corneum) by dissolving the protein bonds (desmosomes) between dead corneocytes. This accelerates natural desquamation, revealing smoother, brighter, more evenly-toned skin beneath. The AHA family includes glycolic acid (smallest molecule, MW 76, deepest penetration, highest efficacy and highest irritation), lactic acid (MW 90, gentler, provides additional humectant benefit, good for dry Indian skin), and mandelic acid (MW 152, largest common AHA, slowest penetration, lowest PIH risk — the best first AHA for Indian skin). AHAs at 5–10% (daily use) improve skin texture by 30–40% at 8 weeks. AHAs at 20–40% (weekly peels) provide more dramatic resurfacing but carry proportionally higher PIH risk in Fitzpatrick III–V skin. Best for: rough texture, dullness, fine lines, mild sun damage, keratosis pilaris, superficial pigmentation. Not effective for: clogged pores, active acne, or oily skin (AHAs cannot penetrate sebum). Critical rule for Indian skin: always start with mandelic acid 5–10% or lactic acid 5% rather than glycolic acid. Glycolic acid's small molecular size causes deeper penetration and greater inflammatory potential, which in melanin-rich skin translates directly to PIH risk. If glycolic acid is desired, build tolerance gradually over 4–6 weeks starting at 5% every other night.

BHA (Beta Hydroxy Acid): pore-penetrating acid for acne and congestion

BHA refers almost exclusively to salicylic acid — the only commonly used beta hydroxy acid in skincare. Unlike AHAs, salicylic acid is lipophilic (oil-soluble), meaning it can dissolve into sebum and penetrate inside the pore lining where comedones form. This unique property makes BHA the first-line topical exfoliant for acne, blackheads, whiteheads, and enlarged pores — concerns that AHAs simply cannot address because they cannot access the interior of the follicle. At 0.5–2% concentration (OTC), salicylic acid dissolves keratin plugs inside pores, reduces sebaceous lipid accumulation, and exerts mild anti-inflammatory activity through prostaglandin inhibition. The anti-inflammatory property is particularly valuable for Indian skin: it reduces the PIH risk that accompanies any exfoliation-induced inflammation. In head-to-head comparisons, BHA 2% causes significantly less PIH than glycolic acid 8% at equivalent exfoliation efficacy for acne-prone skin. Best for: blackheads, whiteheads, clogged pores, oily skin, mild-moderate acne, sebaceous filament reduction. Not effective for: fine lines (BHA does not stimulate collagen), dry skin texture issues (BHA dries skin further), or pigmentation not associated with acne (BHA has minimal melanin-inhibiting activity). Optimal BHA concentration for Indian skin: 1% for sensitive skin, 2% for normal-oily skin. Products with salicylic acid above 2% are available in India without prescription but should be used with caution on Fitzpatrick IV–V skin due to increased irritation potential.

PHA (Polyhydroxy Acids): the gentle giant for sensitive Indian skin

PHAs — including gluconolactone, lactobionic acid, and galactose — represent the newest generation of chemical exfoliants. Their defining characteristic is molecular size: PHA molecules are significantly larger than both AHAs and BHAs, which means they cannot penetrate beyond the outermost layers of the stratum corneum. This sounds like a disadvantage, but for sensitive Indian skin it is the key advantage: surface-only exfoliation means zero inflammatory penetration, near-zero PIH risk, and compatibility with rosacea-prone, eczema-prone, and reactive skin types that cannot tolerate AHAs or BHAs. Additionally, PHAs are humectants — they attract moisture to the skin surface while exfoliating, unlike AHAs and BHAs which have net drying effects. This makes PHAs the only acid family that simultaneously exfoliates and hydrates. Clinical trials comparing PHA (gluconolactone 10%) to AHA (glycolic acid 8%) found equivalent improvement in fine lines and texture at 12 weeks, with 2 times lower irritation scores and 2 times lower PIH incidence in Fitzpatrick IV–V subjects. PHAs are also antioxidants, providing additional free radical protection that AHAs and BHAs do not offer. Best for: sensitive skin, rosacea-prone skin, post-procedure recovery (after lasers, peels), skin that has not tolerated AHAs or BHAs, ageing skin that needs gentle ongoing exfoliation, and as a "starter acid" for Indian women new to chemical exfoliation. Not effective for: active acne (cannot penetrate pores), deep pigmentation (too gentle for significant melanin clearance), or stubborn texture issues (larger molecules limit resurfacing depth). PHAs are best viewed as the "daily maintenance" acid — safe enough for every-day use on even the most reactive skin — while AHAs and BHAs are the "targeted treatment" acids used 2–3 times weekly for specific concerns.

Combination rules and the best acid for every Indian skin concern

Rule 1: never use more than one acid family in the same routine session. Combining AHA + BHA or AHA + PHA in the same application multiplies irritation risk without proportional benefit increase. Rule 2: alternate acid families across different days or AM/PM. Example: BHA cleanser in AM (pore cleansing) + PHA serum in PM (gentle overnight exfoliation). Or: BHA Monday/Wednesday/Friday + AHA Tuesday/Thursday. Rule 3: start with one acid family for 4 weeks before adding a second. This isolates any irritation to a single cause and prevents barrier overwhelm. Decision matrix for Indian skin: Oily skin with acne and blackheads — BHA 1–2% daily (first choice), add mandelic acid 10% once weekly after 4 weeks. Dry skin with texture and dullness — lactic acid 5–10% every other night (first choice), PHA 10% daily as alternative. Sensitive skin with any concern — PHA (gluconolactone 10%) daily (first and potentially only choice). Combination skin — BHA on oily zones (T-zone), PHA on dry zones (cheeks), applied with separate cotton pads in the same routine. Anti-ageing focus — AHA (glycolic acid 5–10%) every other night for collagen stimulation + PHA daily for antioxidant and hydration support. Post-acne PIH — mandelic acid 10% every other night (exfoliates pigmented cells without triggering new PIH) + BHA 1% on active breakout areas only.

Key ingredients · Evidence summary