Acids. They sound terrifying, especially when we link them to skincare (who can forget Samantha in Sex And The City and her acid peel – we’re mentally scarred for life) but they’re still one of the biggest beauty buzzwords.

When Glossier dropped their much hyped Solution exfoliator, £19, it was clear acids were here for millennials too, and Alpha H’s iconic toner Liquid Gold, £33.50, now sells once every minute. 

Where they used to be a bit off limits – used only by skin obsessives, expert facialists and dermatologists – there’s been a huge surge in interest in acids across the skincare board. 

Indeed, Space NK has seen its sales of products containing acids double in the past couple of years because of the demand for faster results and an increased consumer interest in skincare. And the reason for this excitement? Adding acids to your skincare regime pretty much gives instant (and cumulative) results.

“Acids work on superficial layers of skin, dissolving and breaking down the bond of dead skin cells to leave a fresh, even surface layer,” explains facialist Michaella Bolder. 

But not all acids are the same, she warns: “Retinoic acids work on a deeper level of the skin, speeding up cell turnover (and shouldn’t be used in combination with other acids), while L-Ascorbic acid – aka vitamin C – helps to protect the skin against free radicals and environmental pollution. That’s why you need to know what you’re using.”

The increased popularity of acids in skincare products has unfortunately come with issues of misuse, inevitably on account all of the different acids available and confusion as to how they should be used and for which skin type. Dr Jules-Jaque Nabet, aesthetic doctor and medical director at Omniya, is seeing a growing number of people coming to his clinic after experiencing problems related to the overuse of acids. 

“People want instant results but aren’t following the proper instructions given in terms of how often to use an acid and which particular kind. Then they end up with sensitive skin that’s prone to sun damage and inflammation,” he says.

While overuse and potency (facial products containing acids tend to come in percentage strengths) are tricky factors to navigate when you’re casting your eye across a crowded beauty hall, used correctly, acids are one of the biggest beauty game-changers – and a way to transform your skin. But knowing how to tell an AHA (alpha hydroxy acid) from a BHA (beta hydroxy acid) – the former is best for dry skin, while the latter suits normal to oily skin – and if a glycolic acid works best for your skin or if you’re ready for mega high-strength retinoic acid can be complex. 

Whether it’s brightening dull skin, softening fine lines or addressing pigmentation, scroll down to find out the perfect acid match for your skin type – and the best beauty products containing acids you need to add to your routine, to take your skincare game to the next level.

What is azelaic acid?

“Azelaic acid is a naturally occurring dicarboxylic acid found in grains such as rye, wheat and barley,” says Dr Alexis Granite, consultant dermatologist at The Cadogan Clinic.

How does azelaic acid work?

It helps to reduce pigmentation by inhibiting an enzyme called tyrosinase, which is involved in the production of melanin – the pigment that gives skin its colour. It’s also antioxidant, anti-inflammatory and has antimicrobial properties that work well for mild rosacea and acne.

Can azelaic acid be used for all skin types?

Yes: there’s little risk but lots of benefits. It doesn’t damage the skin barrier and it helps stop the growth of abnormal melanocytes (cells that form melanin) linked to melasma, which causes grey-brown patches, usually on the face. Actual skin saviour.

How should azelaic acid be used and how often?

Azelaic acid is more gentle than other acids used in skincare and likely to take longer to be effective, so be patient (use once a day on clean skin). Higher strengths – 15-20% – are available on prescription if pigmentation persists after six months.

Are there any side effects?

Azelaic acid is a mild exfoliant so can cause extra peeling – use with Aesop Elemental Barrier Cream, £43, which uses reparative agents to soothe the skin post-treatment.

The three beauty products below containing azelaic acids are our favourites for tackling pigmentation: 

What is glycolic acid?

The smallest molecule in the AHA family, so it’s easily absorbed by skin.

How does glycolic acid work?

“It fuels epidermal cell renewal, helping get rid of dead cells and stimulating new ones,” says dermatologist Dr Sandeep Cliff-Patel.

Can glycolic acid be used for all skin types? 

It’s not advisable to use glycolic acid if you use acne treatment Roaccutane. Those with sensitive skin should try polyhydroxy acid (PHA), which is good if your skin can’t tolerate AHAs: try Exuviance Soothing Toning Lotion, £28.

How should glycolic acid be used and how often? 

Add glycolic acid to your evening routine. It’s most effective when used regularly, but you need to build up tolerance, so go easy. Glycolic concentration of more than 20% is typically peel level (Sex And The City alert) and 15% is likely to irritate, so start low and work up. 

“A foaming wash is a great introduction as it’s not too strong,” Cliff-Patel adds. Or in the evenings, when your skin is in repair mode, try a cream or ready-soaked pad which stays on the skin longer.

Are there any side effects of using glycolic acid?

A study found it can mildly increase sun sensitivity so use with Kiehl’s Ultra Light Daily Defense SPF50, £38, to nix this issue.

The three products containing glycolic acid below will help buff your skin to perfection: 

What i is L-ascorbic acid? 

The active form of vitamin C is an antioxidant that protects skin from environmental damage, which can cause dull, crepe-like skin.

How does L-ascorbic acid work? 

Victoria Hiscock, production and education specialist at AlumierMD, says, “L-ascorbic has a natural effect on reducing excess pigment production, which leads to brighter and improve skintone.” Sign us up.

Can L-ascorbic acid be used for all skin types?

Yes: it’s one of the few ingredients backed by years of scientific research in which dermatologists and experts agree everyone should be using it.

How should I use L-ascorbic acid and how often? 

Hiscock says L-ascorbic acid should be applied in the morning to make the most of its antioxidant properties. It usually comes in serum or cream form: use the former directly on cleansed skin and the latter after your usual serum, because creams absorb more slowly into skin.

Are there any side effects to using L-ascorbic acid?

Look out for water, or ‘aqua’, in the ingredients list. L-ascorbic acid is hydrophilic (water-soluble), and therefore dissolves in water. It’s also inherently unstable and oxidises when exposed to air or light, so packaging shouldn’t be transparent. Be an acid detective.

These products containing L-absorbic acid get our vote for brightening power: 

What is retinoic acid? 

Retinoic acid is a prescription-strength ingredient proven to prevent and fight visible signs of ageing. Non-prescription strength retinoic acid is called retinol.

How does retinoic acid work? 

“Retinoic acid directly enters the centre of the skin cell,” says Dan Isaacs of Medik8. “It attaches to retinoic acid receptors and triggers a reaction that tells cells to regenerate quickly, resulting in collagen production.” With regular use, this leads to plumper, firmer skin.

Can retinoic acid be used for all skin types? 

Isaacs explains that because it speeds up cellular regeneration it prevents skin ageing in the same way it helps to correct it. “It’s also recommended for acne sufferers as it prevents dead cells clogging pores,” he says. Avoid if you’re pregnant or breast-feeding – no evidence suggests it’s harmful, but there’s also none to suggest it isn’t.

How should I use retinoic acid and how often? 

It’s suitable for nightly use (with a moisturiser but don’t mix with AHAs or BHAs), but introduce to your routine slowly. “Use a low strength – 0.3% at first. Then upgrade to 0.6%, eventually working up to 1%.”

Are there any side effects of using retinoic acid?

Most retinoids aren’t photostable, which means they deactivate when exposed to UV rays. Hence the opaque packaging.

These are the best products containing retinoic and vitamin A acids to use if you want to firm your complexion:  

Main image: Getty