Alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs) are exfoliating acids used to smooth texture, brighten dullness, and help unclog pores. AHAs like lactic and glycolic acid are water-soluble and work on the skin’s surface; BHAs like salicylic acid are oil-soluble and can travel into pores. For dry, dull, and sensitive skin, AHAs—especially lactic acid—can be fantastic brighteners that also improve hydration, while carefully dosed BHA can keep pores clear without harsh scrubbing.

At the skin level, AHAs loosen the bonds (desmosomes) between dead cells to speed controlled shedding, revealing a more even, reflective surface and encouraging fresh epidermal turnover. Lactic acid also acts as a humectant, drawing water into the stratum corneum—useful for dryness. BHAs (salicylic acid) penetrate into oil-lined pores to dissolve built-up sebum and compacted cells, reducing congestion and the appearance of blackheads. Both AHAs and BHAs can help fade the look of uneven tone over time by accelerating the removal of melanin-laden keratinocytes. Choosing the right acid and strength for your skin type is key—start by discover your skin type so you can customize percentages and frequency.

How to Use It

Effective concentrations for sensitive, dry, and dull skin are conservative: lactic acid 5–10% (start 5%), glycolic acid 4–8% (start 5–6%), and salicylic acid 0.5–1% for leave-on products (2% if your skin is already tolerant, or use as a rinse-off for lower irritation). For AHAs to exfoliate, the pH typically needs to sit around 3–4; formulas closer to pH ~3.5–4 tend to be better tolerated by sensitive skin, especially when the acid is buffered. If your skin stings more than a minute or feels tight/shiny for hours after use, reduce strength or frequency.

Layering: On clean, fully dry skin, apply your acid product first or immediately after a hydrating essence if your skin is very reactive. Follow with a barrier-supportive moisturizer rich in ceramides, cholesterol, and fatty acids. A “moisturizer sandwich” (thin moisturizer layer, acid, then moisturizer again) can buffer strong sensations. Pair acids with humectants like glycerin, hyaluronic acid, and soothing agents such as panthenol, allantoin, or centella. Avoid combining with other strong actives on the same night until you establish tolerance—particularly retinoids, benzoyl peroxide, and low-pH L-ascorbic acid vitamin C serums. Alternate nights is a safer strategy for sensitive types.

Frequency: Begin 1–2 nights per week. If no signs of over-exfoliation appear after 2–3 weeks, increase to 2–3 nights per week. Keep BHAs targeted to congested areas (e.g., T‑zone) to protect drier zones. Use primarily at night. If you choose AHA in the morning, keep it mild and always follow with broad-spectrum SPF 30+—acids can make skin more sun-sensitive. Never combine leave-on acids with physical scrubs; that’s doubling up on exfoliation.

Products to Try

Who Should Avoid It

Skip or use extreme caution with AHAs/BHAs if your barrier is compromised (ongoing stinging/burning with bland moisturizers), during active eczema or rosacea flares, perioral dermatitis, or when starting prescription retinoids or oral isotretinoin. If you’re pregnant or breastfeeding, avoid high-strength peels and consult your healthcare provider before using leave-on salicylic acid; many choose gentler options. Safer alternatives for very sensitive or persistently dry skin include polyhydroxy acids (PHAs like gluconolactone or lactobionic acid), azelaic acid 5–10%, lactic acid at the lower end of the range, or mandelic acid for tone and clarity with a larger, slower-penetrating molecule.

Start low, go slow: patch test behind the ear or along the jaw for 3 nights, begin at 1–2 nights per week, and buffer with moisturizer. Commit to daily SPF 30+—brightening and smoothing only “stick” if you protect the fresh skin you’ve revealed. Not sure which acid and strength fit your exact skin type? Visit https://skinguide.beauty to find the right ingredients and build a routine tailored to your skin’s needs.