How to Start Using Acids in Skincare (Without Ruining Your Skin)

Chemical exfoliants are among the most powerful over-the-counter skincare ingredients available. They dissolve the bonds between dead skin cells, revealing smoother, brighter skin underneath. But they also carry the highest risk of over-use damage among everyday skincare ingredients. The right approach is systematic: choose the right acid for your skin type, start slow, and build frequency carefully.

AHA vs BHA vs PHA: Which Should You Start With?

AHAs (alpha-hydroxy acids) — glycolic, lactic, mandelic acid — work on the skin surface. They improve texture, brightness, and uneven tone and are excellent for addressing sun damage. Lactic acid is the most beginner-friendly because it's gentler than glycolic and doubles as a humectant, adding hydration while it exfoliates. Glycolic acid penetrates deeper (smallest molecular size) and is more potent — better for experienced users.

BHAs (beta-hydroxy acids) — primarily salicylic acid — are oil-soluble, meaning they penetrate into the pore lining. They're the first choice for oily and acne-prone skin, blackhead clearing, and congestion. Less suitable for dry or sensitive skin as an introductory acid.

PHAs (polyhydroxy acids) — gluconolactone, lactobionic acid — have the largest molecular size and work only at the very surface. They deliver similar benefits to AHAs with significantly less irritation potential. PHAs are the best starting point for sensitive skin or complete beginners.

Step-by-Step: How to Introduce an Acid

1. Choose your starting acid: Dry/sensitive skin → lactic acid 5% or a PHA. Oily/acne-prone → salicylic acid 0.5–1%. Normal/combination → lactic acid 5–10%.
2. Start once per week at night. Apply after cleansing, to fully dry skin (wait 20 minutes post-cleanse). Apply to the whole face, avoiding the eye area. Leave on — don't rinse liquid exfoliants off.
3. Wait 20 minutes before moisturising. This gives the acid time to work at the correct pH before the next step raises it.
4. Moisturise generously. Chemical exfoliants temporarily increase transepidermal water loss. Barrier-supportive ingredients — ceramides, hyaluronic acid, shea butter — are ideal on exfoliation nights.
5. Wear SPF the next morning. Non-negotiable. AHAs increase UV sensitivity for 24–48 hours after application.
6. Increase frequency slowly. After 4 weeks at once per week with no irritation, move to twice per week. Most people maintain 2–3 times per week long term.

Signs You're Over-Exfoliating

Over-exfoliation is extremely common and often misidentified as a skin type issue. Signs include: skin that feels tight, raw, or unusually shiny; increased sensitivity to other products; redness or stinging that wasn't present before; breakouts atypical for your skin; a feeling of heat or burning on application of previously tolerated products. If any of these occur, stop all exfoliants immediately and focus on barrier repair — gentle cleanser, ceramide-rich moisturiser, and SPF only — for two to four weeks before reintroducing.

What Not to Use on the Same Night as Acids

Never use retinol and AHAs/BHAs on the same night — the combination strips the barrier faster than either alone. Also avoid vitamin C on the same application: both work best at low pH, but their combined irritation potential is high. Use these ingredients on alternating nights — or split morning versus night — to get the benefits of each without stacking irritation risk.