Hydroxy acids: AHA, BHA and PHA at a glance

Acids in skincare

Acids don't necessarily sound like something you'd want to use in skincare. They seem aggressive and bring to mind chemistry lessons and corrosive acids. However, the acids we know from chemistry class are just a small fraction of all acids. Some acids even occur naturally on the skin. These include hydroxy acids such as lactic acid, citric acid, malic acid, and gluconic acid. The skin has an acid mantle, which has a pH value between 4.5 and 5.75 (for reference: a pH value of 7 is considered neutral, anything below that acidic). A slightly acidic environment is therefore perfectly normal and healthy for the skin. When you use acids in skincare products, you can be sure that they either occur naturally on the skin or have a proven positive effect. Furthermore, the permissible concentrations are strictly controlled and must not exceed certain limits. Therefore, the use of acids in skincare is safe.

Why hydroxy acids in particular?

Hydroxy acids are just one type of acid used in skincare. We will, of course, provide information about other acids here in the near future. First, however, we want to focus on the different forms of hydroxy acids and their effects on the skin.

The acids used are actually called hydroxycarboxylic acids, as they are a natural form of carboxylic acids. They are particularly popular in chemical peels, also known as acid peels. Compared to so-called mechanical peels (those with coarse granules in their formulation), they have several significant advantages. Firstly, they only need to be applied, not rinsed off. Secondly, they usually don't irritate the skin at all, whereas scrubbing with mechanical peels (also known as scrubs) can definitely lead to redness and irritation. In some cases, this can even cause micro-injuries to the skin. Furthermore, some mechanical peels use microplastics as granules and are therefore not environmentally friendly. Finally, granular peels only work on the very outermost surface of the skin. Chemical peels, on the other hand, can penetrate deeper and therefore work more intensively.

The following three points speak in favor of hydroxy acids: They exfoliate, they improve the absorption of other active ingredients, and they moisturize.

Let's first look at the peeling effect. This is caused by hydroxy acids breaking down the intercellular connections between corneocytes. As a result, dead cells are more easily shed, revealing new, young cells.

This leads us to the next advantage: Because the dead skin cells are removed, the way is clear for further care products and their active ingredients can penetrate the skin more easily.

With their large molecules, hydroxy acids are particularly good at binding moisture in the upper layer of skin, which leads to their moisturizing effect.

Which hydroxy acids are used in skincare?

In general, the following hydroxy acids are used in acid peels in skincare: alpha hydroxy acids, beta hydroxy acids and poly hydroxy acids.

The abbreviations of the English names are often used to refer to the acids:

AHAs = alpha hydroxy acids

BHAs = beta hydroxy acids

PHAs = polyhydroxy acids

Salicylic acid, a beta-hydroxy acid, has long been known for its positive effects on the skin. Alpha-hydroxy acids are already partly formed by the body's own acid mantle. They are also very popular because they have a significantly different range of effects than BHAs and are particularly well-suited for other skin types and conditions. Poly-hydroxy acids are still relatively new to the field of skincare. In many respects, they are comparable to their relatives, the AHAs, but offer significant advantages, especially in terms of tolerability.

Below we give you an overview of all three types of hydroxy acids and explain how you can use them and which acid is particularly suitable for whom.

 

Alpha hydroxy acids (AHA)

Typical AHAs used in skincare include lactic acid, glycolic acid, mandelic acid, tartaric acid, malic acid, and citric acid. Many AHAs occur naturally in fruits, which is why they are often referred to as fruit acids or marketed as fruit acid peels.

Some of these acids occur naturally on the skin (such as lactic acid), therefore they are generally well tolerated.

Because alpha hydroxy acids (AHAs) have a moisturizing effect, they are well-suited for dry and mature skin. AHAs can also reduce wrinkles and scars. Thanks to their exfoliating effect, they are also effective against blemishes. Even those with balanced skin can benefit from them, and AHAs can even help with rosacea; mandelic acid, in particular, is an excellent choice in this regard. However, a dermatologist should always be consulted for skin conditions. Unlike beta hydroxy acids, AHAs can also be used in the routines of pregnant and breastfeeding women.

AHAs are helpful for a whole range of minor and major skin problems. They can smooth flaky skin and soothe reddened areas. In addition to their slow-aging effect against wrinkles, AHAs also lighten age spots and other pigmentation marks. Even scars from past acne can be improved. Alpha hydroxy acids also provide relief for acute sun damage.

Glycolic acid is particularly beneficial for sun-damaged skin. It stimulates collagen production and provides moisture, making it especially helpful for dry, flaky skin. Lactic acid also has a moisturizing effect and additionally leads to increased ceramide production. It is particularly well-suited for dry and sensitive skin.

Alpha hydroxy acids are water-soluble and therefore cannot penetrate very deeply into the skin. They thus only act on the outermost layer of skin, the epidermis.

As with most active ingredients, there are of course some things to consider when using acids, and side effects can occur. In rare cases, irritation can occur, and sensitive skin may react with dryness. Generally, you should introduce AHAs, like all new active ingredients, gradually. Regarding other active ingredients, it's important not to combine acids directly with vitamins A and C, as well as with niacinamide. However, there's nothing wrong with using these substances on different days or at different times of day. Furthermore, you should avoid applying acid peels containing AHAs near the eyes or on mucous membranes. Sunscreen should also be an essential part of your daily morning routine when using AHAs, as they increase sensitivity to UV radiation.

We especially recommend AHAs for dry, sensitive, and damaged skin. They combine well with other moisturizing and plumping ingredients. Hyaluronic acid is a prime example. AHAs, like those in our Exfoliate Booster, are particularly well-suited for combination with the following products from our range:

• Hyaluronic Acid Booster
• Barrier Booster
• Calming Moisturizer
• Rich Care & Rich Night Moisturizer
• Organic jojoba oil

Beta hydroxy acids (BHA)

The only truly relevant beta-hydroxy acid in skincare is salicylic acid . Therefore, the term BHA is often simply used synonymously with salicylic acid. In skincare products, it may only be present in a maximum concentration of two percent. This sounds like a very low amount, but it is perfectly sufficient. Its effectiveness at this concentration has been proven in studies.

Salicylic acid is generally well tolerated. However, if you have an allergy to acetylsalicylic acid (also known as ASA), you should definitely not use it.

Beta-hydroxy acids (BHAs) are fat-soluble and can therefore penetrate even into the second layer of skin, the dermis, where they effectively dissolve sebum. This makes BHA an excellent active ingredient for oily, combination, and generally blemished skin. Thanks to its anti-inflammatory and exfoliating properties, salicylic acid is also beneficial for pimples and blackheads. Furthermore, it has a soothing and regenerative effect on the skin.

BHA can also improve keratosis pilaris and hyperpigmentation, and even help with calluses and warts. The acid can also be used as a supportive treatment for skin conditions such as acne, rosacea, perioral dermatitis, and psoriasis. However, as with all skin conditions, consulting a dermatologist is advisable.

Acid peels containing salicylic acid can cause the same side effects as those containing AHAs: irritated or dry skin. BHA should also not be used in combination with vitamins A and C or niacinamide. As with AHAs, using it at different times is generally safe. For safety reasons, BHA should be completely avoided during pregnancy and breastfeeding. As with alpha hydroxy acids, salicylic acid should be gradually integrated into your skincare routine.

Products containing BHA are the classic recommendation for blemished, oily, and combination skin. They complement other salicylic acid-containing and sebum-dissolving products particularly well. Our unbeatable BHA trio at colibri is the combination of Purifying Gel Cleanser , BHA Mask , and the 2% BHA Peeling .

 

Polyhydroxy acids (PHAs)

The best-known polyhydroxy acid (PHA) in skincare is gluconic acid. Other relevant acids include lactobionic acid and glucono-delta-lactone. The concentration of PHAs in skincare products varies between 2 and 15%.

PHAs are exceptionally well-tolerated. This makes them the perfect introduction to chemical acid peels if you're still unsure which acid is best suited to your skin.

Like their relatives, the AHAs, polyhydroxy acids (PHAs) are water-soluble and therefore act on the outermost layer of skin. PHAs work very similarly to AHAs, but due to their larger molecular size, they penetrate less deeply and are thus gentler on the skin, making them particularly suitable for sensitive skin. They could even be described as an even more tolerable alternative to AHAs. Because PHAs are so universally tolerated, they can be used without hesitation by all skin types. Only those with an autoimmune disease should avoid products containing PHAs. They are also not suitable for severely aged or damaged skin.

PHAs have a positive effect on the production of collagen and hyaluronic acid in the skin. They moisturize, plump up wrinkles, and reduce the appearance of scars. Their exfoliating effect also improves the absorption of other active ingredients. Furthermore, they stimulate blood circulation and aid skin regeneration. Existing age spots become lighter with PHAs, and their mild antioxidant effect slows the formation of new pigmentation damage. The use of polyhydroxy acids can also have a positive effect on acne. However, as with any skin condition, a doctor should be consulted beforehand.

Unlike AHAs and BHAs, polyhydroxy acids (PHAs) are not known to cause any side effects. Compared to alpha hydroxy acids, PHAs are much less likely to cause burning and redness. Polyhydroxy acids are less photosensitive than other hydroxy acids and are therefore even suitable as a daytime exfoliant, for use in the morning, or especially during the sun-intensive summer months. Of course, you should still wear sunscreen . If you want to incorporate PHAs into your morning routine, it's recommended to do so between cleansing and applying antioxidant serums such as vitamin C and niacinamide . Just like AHAs, products containing polyhydroxy acids can also be used during pregnancy and breastfeeding.

In general, PHAs can be combined with all other active ingredients. For a more intensive peeling effect, and due to their similar range of effects, they are often combined with alpha hydroxy acids, for example. It's important to be careful not to overwhelm the skin with too many peeling treatments, as this can lead to irritation. To better protect the skin from sun exposure and reduce signs of aging, combining PHAs with vitamins C and E is effective. We particularly recommend our two Vitamin C Boosters or our Jojoba Oil , which is very rich in Vitamin E. PHA products can also be combined very effectively with other acid peels, such as the Exfoliate Booster or our 2% BHA Peel .