Acids - they’re the miracle tools used to fight acne, wrinkles, age spots, scarring, and uneven skin tone. But with so many acids on the market, it can seem overwhelming to remember which to use — and for what — and which products to buy. It's important to know what each does. So we've put together a list of the most common ones, along with why to use them.
Salicylic acid has been around for a long time. It’s well-known for its ability to exfoliate the skin and keep pores clear, which helps reduce acne. You’ll find it in serums and cleansers at concentrations between 0.5 and 2 percent, as well as in spot treatments for breakouts.
Salicylic acid is also used in higher concentrations as a peeling agent for treating acne, acne scars, melasma, sun damage, and age spots in dermatology clinics. It’s so effective that it’s used in wart and corn removal solutions, although it’s still safe to use in pigmentation-prone dark skin. Since it’s related to aspirin (acetylsalicylic acid), it also has anti-inflammatory properties.
Glycolic acid is the most popular alpha-hydroxy acid (AHA) used in skin care. It comes from sugar cane, and is the smallest AHA, so it’s the most effective at getting into the skin. Glycolic acid is a fantastic anti-aging agent that seems to do it all.
It’s very effective at exfoliating skin and reducing fine lines, preventing acne, fading dark spots, increasing skin thickness, and evening out skin tone and texture. So it’s no surprise that you find it in many different skin care products. It’s commonly found at concentrations below 10 percent.
Much like salicylic acid, glycolic acid is also used in peels for treating acne and pigmentation, sometimes in tandem with microdermabrasion or micro-needling. However, use of glycolic acid increases sun sensitivity even when it’s not on the skin, so you need to use sunscreen as well to prevent extra sun damage.
Hyaluronic acid adds volume to the skin, calms the skin and maintains skin's moisture. Hyaluronic acid, also known as hyaluronan, is a clear, gooey substance that is naturally produced by your body. The largest amounts of it are found in your skin, connective tissue and eyes. It binds to water to help retain moisture. As we age, our body products less hyaluronic acid, so applying it to your skin daily can reduce the look of wrinkles, redness and make skin appear smoother.
Mandelic acid is another alpha-hydroxy acid, one that’s derived from bitter almonds. Like glycolic acid, it’s an exfoliating agent that’s useful for preventing acne, treating sun damage, and evening out pigmentation.
However, due to its larger molecular structure, it doesn’t penetrate skin as deeply as glycolic acid, so it’s less irritating to the skin. For this reason, it’s commonly recommended in peels instead of glycolic acid, particularly for ethnic skin which is more prone to rebound pigmentation. (Rebound pigmentation occurs when a resistance is built up to a particular substance due to excessive use. This causes the substance to not only be ineffective, but often causes it to have the opposite of the intended effect.)
Azelaic acid has been one of the mainstay treatments for fighting moderate acne for the last three decades, and is found in many prescription-only creams. It keeps pores clear, kills bacteria, and reduces inflammation. It’s generally found at 15 to 20 percent concentrations in creams that are designed to be applied all over the face, morning and night. Azelaic acid generally has very few side effects, but in some people with very sensitive skin it can cause stinging, peeling, and redness.
As well as treating acne, azelaic acid is also a skin-lightening agent that’s useful for fading post-acne marks, or post-inflammatory hyperpigmentation. It’s frequently combined with retinoids as a milder alternative to hydroquinone.
Kojic acid is produced by bacteria used in the fermentation of rice for the production of sake. It’s a popular ingredient in Asian skin care products thanks to its whitening and anti-aging properties
It’s found in cleansers and serums at 1 to 4 percent concentrations. Unfortunately, it’s very irritating to skin — but it’s also very effective.
Ascorbic acid is the most common water-soluble form of vitamin C, and is used in skin care for its anti-aging effects. It’s also been used as a substitute for hydroquinone in treating melasma. Ascorbic acid is very unstable in the presence of oxygen and water, so it’s commonly available in more stable forms under the name magnesium ascorbyl phosphate and tetra-isopalmitoyl ascorbic acid.
Many acids offer multiple benefits and since they can come in many different formulations it’s possible to use more than one. Brands will often advertise the active acids in cleansers, serums, toners, and more, but check the ingredient list to make sure the acid is the active ingredient — listed near the top, and not a forgotten side character at the very end of the list.
Don't mix your acids, instead use one in the morning & another at night:
- Don’t use salicylic acid with any other acid at the same time. Extreme skin irritation may occur when mixed.
- Avoid salicylic acid with products that contain niacinamide.
- Don’t use glycolic acid or lactic acid in combination with ascorbic acid (vitamin C). This will cause the ascorbic acid’s benefit to disappear even before it begins to work.
- Avoid using AHAs with retinol.