13th August 2022

The Only Guide to Skincare Acids You Need

Last Modified: August 19, 2022

Acids are probably the last thing you would want to put on your face, right? Well, not exactly. While it might initially sound intimidating, acids should be a staple in everyone’s skincare regimen.

Read on, to learn all about acids and find the right ones for your skin type and concerns.

When formulated correctly, these work effectively to target dull tone, dark spots, hyperpigmentation, fine lines and more.

We will also break down the acids by structure, exploring how they function and how you can pick the acids best suited to your skin concern.


Alpha hydroxy acids (AHAs) are a group of acids derived mainly from plant and animal sources, although some are produced in the lab.

AHAs are water-soluble, which means they cannot penetrate the skin's natural oils. 

For this reason, their primary role is to exfoliate the stratum corneum (the outermost layer of the skin).

Exfoliation is an important skin care process that strips away the dead skin cells on the surface to make room for new skin cells to form. 

This is very important because a build-up of too many dead skin cells will make your complexion look sallow while exacerbating other skin problems, such as wrinkles and acne. 

Common AHAs include glycolic acid, lactic acid and mandelic acid.

Glycolic acid

Glycolic acid, which is derived from sugar cane, is the smallest of the alpha hydroxy acids, weighing about 76 daltons. Due to its low molecular weight, it acts on both the epidermal and dermal layers, making it the most effective AHAs exfoliant. 

It also regulates matrix degradation associated with photo-ageing and increases the thickness of the epidermis. It has antibacterial properties when formulated under a pH of 4.00 and brightens the skin by not only increasing cell turnover but also acting as a tyrosinase inhibitor.

Because of all its amazing benefits, glycolic acid has earned a place in our blog on active ingredients that are safe for pregnant women.

Lactic acid

Lactic acid is usually derived from the lactose found in milk, but can also come from fructose. This skin-smoothing and moisturising alpha hydroxy acid is known for its gentle exfoliating action.

It is a larger molecule than glycolic acid, which means it penetrates the skin less and is therefore less likely to cause irritation.

Lactic acid has been shown to be effective in treating photo-ageing, hyperpigmentation and dark spots, dry skin and mild skin breakouts.

Mandelic acid

Mandelic acid has twice the molecular weight of glycolic acid (152 Daltons), so it penetrates the skin more slowly.

Therefore, mandelic acid is less likely to cause irritation - even in people with sensitive skin and deeper skin tones. But be sure to do a patch test before applying it all over your face.

Mandelic acid's powerful antibacterial properties combined with its gentle exfoliating abilities combat acne, dull skin, uneven texture and hyperpigmentation.

Studies have also shown that mandelic acid can boost collagen production, which over time improves skin elasticity and slows the formation of fine lines and wrinkles.

How to use AHAs

How often you use alpha hydroxy acids depends on the particular acid, the product and your skin. 

A good rule of thumb is to choose a product that contains lower amounts of different types of AHAs, rather than using an extremely high amount of just one type. While a high potency of a single acid can give remarkable results, combining different AHAs in lower strengths might prove to be more suitable for long-term use.

That's because it can be less irritating as they penetrate and exfoliate the skin to different depths. In addition, the type of product and the condition of your skin also play a role. You will find AHAs in everything from cleansers to creams.

People with sensitive skin might choose to start with a cleanser rather than jumping straight into a cream with more potent active ingredients. It's always best to start slowly and gradually increase the frequency of use as your skin can tolerate it.

And always remember: never exceed the frequency stated in the instructions.

Which AHA product should you buy? Click here for our recommended skincare brand


Beta hydroxy acid, is another acid that derives from plants, is a common ingredient in skincare products, especially those for treating acne. Really the only beta hydroxy acid (BHA) used in skin care is salicylic acid. So if products contain a BHA, this is probably what it's referring to. 

This beta hydroxy acid offers similar benefits to alpha hydroxy acids, including exfoliating, reducing hyperpigmentation and smoothing skin texture.

However, unlike AHAs, BHAs are oil-soluble, meaning they can penetrate deeper into the pores and help clean out and dissolve excess sebum build-up.

If you tend to have oily, blemish-prone skin, salicylic acid is a great acid to have in your skincare arsenal.

Thanks to its hydrophobic property, salicylic acid can work in the pores to remove excess sebum and debris, making the skin less clogged and potentially making pores smaller.

It is also known for its antibacterial and anti-inflammatory properties which also help prevent acne breakouts.

 How to use BHAs

Although salicylic acid is a widely used skincare ingredient that is readily available, you should still approach it with caution.

The use of salicylic acid depends on the skin type, the underlying indication and the severity of the acne. This is because salicylic acid is not one-size-fits-all.

It is best to have your skin assessed by a medical aesthetician to decide how best to incorporate this BHA into your skin care regimen.

The recommended concentration of a salicylic acid product Once you get the product home, pay attention to how your skin reacts after each application. "The most important thing is to listen to your skin. "If it's getting irritated, maybe take a break for a day or two.

Which BHA product should you buy? Click here for our recommended skincare brand


We all can achieve radiant, glowing skin from regular exfoliation. That said if you have sensitive skin - and especially if you are prone to rosacea or eczema - you may find chemical exfoliants like alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs) can be too harsh.

However, that does not mean you should give up acids, at least until you try polyhydroxy acids (PHAs). 

The prefix "poly" means "many", and so polyhydroxy acids have two or more hydroxyl (pairing of oxygen and hydrogen atoms) in the molecule.

This means they can offer similar benefits to the skin as AHAs, but with some added benefits. PHAs are larger molecules than AHAs, so their penetration into the skin is limited and gradual, which means less irritation for people with sensitive skin. 

The numerous hydroxyl groups also attract water and provide additional hydration to the skin (a great benefit for people whose skin dries out easily in winter).

Their antioxidant properties also help prevent oxidative damage from UV exposure, poor diet and age-related skin changes such as skin sagging. 

The best-known PHAs are:

Gluconolactone: exfoliates your skin, moisturises and provides some antioxidant benefits.

Lactobionic acid:  produced from oxidised milk, this acid acts as both an exfoliant and a humectant (helps your skin retain moisture).

Galactose: It is not as common as the other two, but it works just as gently as an exfoliant for your skin.

PHAs can enhance the therapeutic benefits of active ingredients and are therefore often mixed in skin care products as more of a supporting player..

How to use PHAs

This largely depends on what type of product you use and what other ingredients are included. Moisturising products can be used up to twice a day. However, if you're using more of an exfoliating product such as a scrub or serum, limit yourself to a few times a week. 

Also, note that PHAs work synergistically with other acids and retinoids and can be alternated for maximum effect.

Also, it's a good idea to pair any product with PHAs with an extra layer of your favourite moisturiser: Because PHAs are humectant, they draw the water from the moisturiser into your skin for an extra boost of hydration.

Post Reviewed by: Dr Baldeep Farmah
Medically Reviewed on: 13th August 2022
Dr Baldeep Farmah is the Medical Director and lead Doctor of Dr Aesthetica, a Medical Aesthetic Clinic.

"We want to empower everyone who walks through our clinic doors, to be able to look in the mirror and see a happier, brighter version of themselves."

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