Skincare Acids: Types, Benefits, And How To Choose The Best One

Everything You Need To Know About Skincare Acids

Acids are some of the hottest ingredients in skincare right now but with so many types, it can be tricky to decode. Here’s a crash course in everything you need to know about skincare acids. 

1. Exfoliating Acids

When it comes to unlocking glow, alpha-hydroxy acids (AHAs) are the Holy Grail. “AHAs are hydrophilic, ‘hydro’ meaning water, and ‘philic’ meaning loving,” explains Victoria Hiscock, product specialist at AlumierMD. “They interact with water molecules in the upper layers of the skin, which triggers an [exfoliating] effect.” So, which AHA is best for you? Glad you asked!

Glycolic Acid

Best for: Fine lines

This one has the smallest molecules of all the AHAs, so it penetrates the deepest and fastest. “Studies show it helps to initiate collagen synthesis and boost hyaluronic acid [more on that later] in the lower skin layers, plumping fine lines and wrinkles,” says Paula Begoun, dermatologist and founder of skincare brand Paula’s Choice. Glycolic acid is so ruthlessly efficient that it only takes one application to yield results. The downside? It works so quickly that skin can become irritated. This is where percentages come in – the higher the strength, the more likely irritation will occur. If you’re a glycolic virgin, start with formulations between three and five per cent. “These will hit the sweet spot for daily use, because any irritation will be very minimal and will subside after a few applications,” says Dan Isaacs, head of research and development at skincare brand Medik8. “You’ll know, because the tingling sensation will disappear. However, be sure to give your skin regular breaks. So, use one bottle of product, then have a month off.” Once your tolerance rises, you can use stronger formulas, around 10 per cent. Anything higher is best as a one-off treatment. Watch pH levels, too. Some brands will formulate their glycolic acid with a high pH level to counteract potential irritation, but this also weakens the acid. The ideal pH level for glycolic should be three to four. This means the acid percentage stated on the label will be true to form. “PH levels aren’t always stated on the label, so check the website,” adds Isaacs.

Lactic Acid

Best for: Dry skin

Remember the tale of Cleopatra bathing in milk? Well, she was way ahead of the game because sour milk produces lactic acid. Now created synthetically in a lab, this AHA is gaining a following because its molecules are bigger than those in glycolic, so they don’t penetrate as deeply to trigger that peeling action. If you have dry or sensitive skin, this is a good thing. “At low percentages, about five per cent, lactic acid also acts as a humectant, drawing moisture into the skin while it exfoliates,” says facialist Kate Kerr. It won’t provide dramatic overnight results on its own, so if you want instant effects, opt for a formula that combines lactic with glycolic acid and plenty of antioxidants. This will still be weak enough not to cause irritation, but strong enough that you’ll notice a difference. In Murad Age Reform AHA/BHA Exfoliating Cleanser ($62), lactic, glycolic and salicylic acids (we’ll explain that last one soon) work to smooth skin and clear out pores. 

Mandelic Acid

Best for: Pigmentation and acne

Research in Dermatologic Surgery showed this was as effective as glycolic at treating pigmentation from sun damage, but with less redness and irritation. And further studies suggest it also reduces melasma by as much as 50 per cent in four weeks. Like other AHAs, mandelic’s micro-exfoliating properties help lift excess pigment from the skin’s surface. Its gentle approach also makes it a winner for those with darker skin tones, who should avoid glycolic and lactic acids because the irritation they cause can lead to post-inflammatory hyperpigmentation. “This is because there’s more melanin in the skin, which means there are also more melanocytes to react to irritation and trigger excess pigmentation,” explains Dija Ayodele, facial aesthetician and founder of the Black Skin Directory. Mandelic is also championed by cystic acne sufferers. “As well as exfoliating, it also has antibacterial properties, which help to regulate sebum production,” says Dr Wei Chen, senior research and development manager at Dermatologic Cosmetic Laboratories. This stops acne forming. Products with five per cent mandelic acid will be gentle enough for daily use. “If the formulation contains 10 per cent mandelic acid, it should be applied two or three times a week, always in the evening,” says pharmacist Shabir Daya. Why at night? AHAs increase your skin’s sensitivity – so don’t forget to apply your daily SPF.

Salicylic Acid

Best for: Oily skin and acne

It’s not just AHAs that will exfoliate your skin – salicylic is a beta hydroxy acid (BHA), and it’s kryptonite to acne. “It’s the only acid able to infiltrate the pore lining, so it can flush out dirt, dead cells and trapped sebum,” explains Begoun. This quickly restores oil flow out of the pore, so it’s less likely to get clogged with the debris that leads to blackheads, whiteheads and acne. Strengths of 0.5 to two per cent are usually gentle enough for use at home.

Polyhydroxy acids

Best for: Sensitive skin

Just as you get a grip on AHAs and BHAs, we add in polyhydroxy acids (PHAs), such as those in the Ole Henriksen PHAT Glow Facial ($68). While they may not have the same deep-down exfoliating skills as AHAs, PHAs boast other benefits. Gluconolactone is the most powerful type – it’s also an antioxidant and has properties that protect skin from pollution and UV damage. A powerful humectant, it keeps the skin well hydrated and impedes elastase, an enzyme that causes sagging.

best exfoliating acid serums


best glycolic acid cleanser

Peter Thomas Roth

best face masks

The Ordinary

2. Moisturising Acid

Hyaluronic Acid

Best for

All skin types Hyaluronic acid occurs naturally in the body and hydrates the skin by binding water to collagen. It’s a magnet for moisture, drawing it from the environment to keep cells plump and healthy. Adding it your skincare arsenal is paramount because, as you age, your skin becomes dehydrated more easily.

3. Treatment Acid

L-ascorbic Acid

Best for

Free-radical damage L-ascorbic acid (vitamin C, to its mates) is a potent antioxidant that wards off free-radical damage caused by environmental factors such as sun exposure and pollution. If vitamin C had a star sign it would be Gemini, because it’s utterly two-sided. On one hand, L-ascorbic acid is the strongest form of vitamin C when it comes to dealing with sun damage and fine lines, yet, it’s also the weakest, because once it comes into contact with air and heat it oxidises, rendering it useless. Therefore, a stable five per cent vitamin C serum will be more effective than an unstable 25 per cent serum. How can you spot stable formulations? The packaging is key. Lancôme Visionnaire Skin Solutions Vitamin C 15% ($115) comes in two 10ml bottles, which reduces contact with air each time one is opened. Stable formulations won’t contain water, either.

What not to do with acids

Fears about AHAs aren’t totally misplaced. “I’ve seen a rise in patients coming to me with concerns about irritation from overusing or misusing acids,” says skincare expert Dr Sarah Shah. Her advice? If you haven’t used acids before, start by working one into your routine with a wash, such as Peter Thomas Roth Glycolic Acid Cleanser ($59). “This limits the amount of contact time with your skin and avoids over-drying.” Then you can move on to a serum or peel pads. Just make sure you’re only using one acid-based product in your regimen. “You also don’t need to start on a single acid first [products containing a mix of acids are fine], but it’s beneficial to help you understand which ones work best on your skin type,” adds Isaacs.

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