Guide
What is a chemical exfoliant and how do you use it?
Your skin produces new cells every day and pushes old ones to the surface. When this cycle slows down, dead cells build up: skin looks dull and rough, and pores clog easily. Exfoliants remove this build-up. Acid products used at home are called chemical exfoliants, and when used correctly they give a far gentler and more even result than gritty scrubs.
Where it fits in your routine
- Cleanse
- Tone
- Treat
- Moisturize
- Protect
AHA vs BHA vs PHA
AHAs (alpha hydroxy acids) are water-soluble and work on the surface of the skin. Glycolic acid has the smallest molecule, making it the most effective AHA but also the one most likely to sting; lactic acid is gentler and more hydrating, and mandelic acid, with its large molecule, is favoured for sensitive skin. AHAs help with roughness, dullness, fine lines and sun spots.
In skincare, BHA means salicylic acid. Because it is oil-soluble it can travel into the pore; it is the best option for oily skin prone to blackheads, whiteheads and breakouts. PHAs (gluconolactone, lactobionic acid) are the largest and gentlest group, and a good starting point for sensitive or rosacea-prone skin.
Chemical or physical exfoliation?
Physical (mechanical) exfoliants remove dead cells by scrubbing, with gritty creams or brushes. Large, irregular particles (such as ground nut shells) can cause micro-tears on the skin's surface and increase irritation, especially when you have active acne or sensitivity.
Chemical exfoliants dissolve the bonds between cells for a more even shedding. That is why dermatologists usually recommend low-strength chemical exfoliants for home use. If you love a scrub, choose one with very fine, rounded particles and use it once a week with a very light touch.
Choosing by skin type
- Oily, blackhead- and acne-prone skin: salicylic acid (BHA) toner or serum
- Dry, dull and rough skin: lactic acid or low-strength glycolic acid
- Sun spots and fine lines: glycolic acid; morning sunscreen is essential
- Sensitive and rosacea-prone skin: PHA or mandelic acid; do not use at all if your skin is irritated
- Dark spots and acne marks: azelaic acid is both a mild exfoliant and a dark spot fighter
How to use it, and how often
Apply the acid product in the evening to cleansed, dried skin. Use toners with a cotton pad and serums with a few drops; stay away from the eye and lip area. Start with one or two evenings a week; after two or three weeks, if your skin is comfortable, go up to three or four evenings. Daily use is only for low-strength, gentle products once your skin is fully used to them.
With rinse-off peel masks, always stick to the stated time; leaving them on longer does not increase the benefit, it increases irritation. While using acids and for a week afterwards, wear a broad-spectrum sunscreen every morning: AHAs increase the skin's sensitivity to the sun.
Do not layer retinol and acids on the same night. A schedule such as acid on Monday and Thursday, retinol on other nights and just moisturizer in between is much easier on the skin.
Signs of over-exfoliation
The most common mistake with acids is thinking more is better. When the barrier is damaged, skin can actually look duller and more problematic.
- Even your usual moisturizer stings or burns
- Persistent redness, tightness and flaking
- Skin that looks waxy, overly shiny and "plastic"
- Small breakouts and sensitivity that were not there before
- If you notice these signs, stop all acids and retinoids and use only a gentle cleanser, moisturizer and sunscreen for one or two weeks
FAQ
How many times a week should I exfoliate?
Once or twice a week to start. If your skin adjusts without irritation, you can go up to three or four times a week. High-strength rinse-off masks should stay at once a week.
Can I use acids in summer?
Yes, but SPF 30–50 every morning and reapplying during the day are essential. If you will be in the sun for long periods or are on holiday, pausing acids is the safer option.
Can I use salicylic acid and glycolic acid together?
Some products contain both and are well tolerated by some skin types. But using them on different evenings, rather than layering two separate acid products, lowers the risk of irritation.
Can I use chemical exfoliants during pregnancy?
Low-strength glycolic, lactic and azelaic acid are generally considered acceptable. High-strength and large-area salicylic acid applications are avoided. During pregnancy, check every new product with your doctor.
This article is for general information only and is not medical advice. If you have a skin condition, are pregnant or take regular medication, talk to your dermatologist or pharmacist before starting a new product.
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