Everyone knows them, has heard of them, and has probably used them. But what exactly are skincare acids? And how and when should you use them? We know that using acids on the face seems daunting at first, but in fact, all skin types can benefit from incorporating acids into their skincare routine. There are different types of acids for any skin condition you want to treat, from acne, hyperpigmentation, dehydrated skin, wrinkles and fine lines to sensitive skin. Depending on the skin condition, different acids might be more effective, so be careful which acid you use if you want to achieve optimal results. But which acid is suitable for which skin problem?

What types of acids are most commonly found in skincare products and how do they differ?

They are roughly divided into alpha-hydroxy acids, beta-hydroxy acids, and polyhydroxy acids which differ mainly in the degree of their penetration into the skin and the nature of their effect on the skin.

Alpha Hydroxy Acids (AHA) 

These are the most commonly used acids and include Glycolic, Citric, Mandelic, Malic, Tartaric and Lactic. They exfoliate the skin, stimulate collagen and GAGs (glycosaminoglycans) formation. They normalise the stratum corneum (the outer-most layer of the epidermis) and can regulate keratinization. Alpha hydroxy acids (AHAs) are known for their water soluble properties, so they work on the skin’s surface. They are mostly used on normal to dry, sun-damaged skin, due to their ability to enhance natural moisturising factors within the skin. What is also really great about AHAs, that they have evidence based effects on reducing sun damage, smoothing fine lines and wrinkles, exfoliating dead/dull looking skin cells and thereby making the skin appear smoother and glowing! When the dead skin cells are removed, the active ingredients applied can absorb better, making the most out of your skincare routine.

Included in: Better Aging Body Lotion

Beta Hydroxy Acid (BHA)

There is only one beta hydroxy acid – salicylic – derived from acetylsalicylic acid, or aspirin. Like AHAs, beta hydroxy acid (BHA) also acts as an exfoliant increasing the shedding of dead skin cells. BHA is extremely useful for treating breakouts and helps manage keratosis pilaris and other conditions that involve blocked or clogged pores. BHA works on both the skin’s surface and deep inside the pores. It’s oil soluble, so is best suited for normal to oily skin prone to bumps, clogs, blemishes and enlarged pores. BHA also has natural skin-calming properties, so it’s gentle enough for skin that's sensitive or prone to redness or rosacea. This well-rounded, gentle ingredient is even suitable for bumpy skin prone to milia, while improving the look of dull, dehydrated skin.

Included in: Purity Body Lotion

Polyhydroxy Acid (PHA)

Gluconolactone & Lactobionic Acid Polyhydroxy acids (PHA) are next-generation Alpha Hydroxy acids, with the properties to exfoliate skin cells. It has larger molecules, therefore it cannot penetrate as deeply. PHAs are great for pigmentation, mild exfoliation and hydration. PHAs support the matrix around collagen, help restore skin barrier function and protect against collagen degradation. PHAs are probably the most multi-tasking of all acids. Gluconolactone, lactobionic and maltobionic are examples of PHAs. Best for signs of aging and sensitive or dehydrated skins.

Included in: Purity Body Lotion

What’s the main difference between AHAs and PHAs?

• AHAs are water soluble so they do not penetrate deeply beneath the skin’s surface. BHA is oil (lipid) soluble. This allows the BHA to penetrate oily pores and help to exfoliate the pore itself. This is why salicylic is particularly helpful when used on oily and acnaic skins. However, in order to work effectively, AHA and BHA exfoliants should have a pH value between 3 and 4.
• PHAs tend to be better for sensitive skins due to their larger molecular size and slower penetration. PHAs are great humectants on the skin, making them particularly good choices for dehydrated skins.

Which acid is best for which skin type?

Salicylic Acid

Derived from willow bark, salicylic acid is oil soluble and penetrates and breaks down the ‘glue’ that causes breakouts and oily, uneven skins. It loosens desmosomes allowing the cell to let go of the excess sebum that oily skins like to hold on to. Think of desmosomes as handcuffs, attaching your cells together. Salicylic unlocks the handcuffs. Even those new to acids will probably have heard of salicylic acid. It’s the hero acid for those with acne-prone skin because it penetrates pores to reduce sebum.  What’s more, it can remove discoloration and improve skin tone over time and can also be effective for treating rosacea. Verallo-Rowell points out that it’s the only beta hydroxy acid (BHA) and it’s not for those who are pregnant, breastfeeding or allergic to aspirin. Those with darker complexions should also watch out because it can sometimes cause irregular lightening or darkening of skin.

Glycolic Acid

Containing the smallest molecule in AHAs, glycolic is derived from sugarcane and is the most effective AHA due to its ability to penetrate deeply and stimulate fibroblast cells to aid in collagen production. It exfoliates the skin by increasing cell turnover, evens skin tone and builds the support structure in the dermal matrix reducing wrinkles. It is the only acid that makes you sun sensitive. Glycolic acid is a versatile AHA that can help improve the appearance of spots, scars and wrinkles while making skin more radiant. Plus, it will shrink pores. Dr Natalie says that it’s one of the best acids for aging skin.

Included in: Better Aging Body Lotion 

Lactic Acid

Lactic acid is a key ingredient to remember for sensitive skin types. The acid exfoliates and softens fine lines and wrinkles, but in a less irritating way than other acids says Imahiyerobo-Ip. Historically derived from milk, more recently synthetically formed to maintain stability, lactic works to dissolve the glue in between cells on the surface making it good for gently exfoliating. It keeps the skin soft and acts like Pac Man on the surface of the skin, gently eating it away.

Included in: Smooth Body Lotion

Mandelic Acid

Mandelic acid is an AHA derived from bitter almonds but  is more gentle than some of the other AHAs like glycolic acid. Mandelic acid is ideal for brightening and lightening skin. According to Verallo-Rowell, the acid comes from grapes and has fairly high acidity, but it’s less irritating than glycolic acid. It’s a common peel ingredient so look for it in at-home and professional peels. It is a good choice for oilier skins, as the molecules can penetrate even the greasiest of skins. Mandelic is antibacterial and can reduce oiliness with regular usage without harshly drying the skin out.

Included in: Glow Body Lotion

Azelaic Acid

Those with redness often fear harsh skin care ingredients like acids. There’s no need to be scared of azelaic acid. Imahiyerobo-Ip says that the acid can benefit those with redness, rosacea and acne. It’s also suitable for treating hyperpigmentation and melasma.

Included in: Purity Body Lotion

Citric Acid

Citric reverses signs of photo damage while also improving the quality of the dermal matrix. It can sometimes only be used at preservative level just so brands can claim it on the label. Look for specific mentions of citric in the descriptions on packaging, if they’re not there, it’s probably a preservative only.

Tartaric and Malic Acid

Mainly derived from grapes/apples/pears and cherries, these two are more gentle on the AHA scale but do act as antioxidants and aid skin respiration.

Once you have found an acid that suits your skin type, make sure you use it correctly. For example, you should preferably apply it at night and use it sparingly during summer vacations, because acid makes the skin more susceptible to UV radiation. For this reason, adequate sun protection is especially important.