Introduction
When it comes to modern dermatology, acids are among the most powerful and widely used active ingredients in skincare. From gentle exfoliation to acne treatment and anti-aging benefits, each type of acid has its function. Additionally, each type of acid has its own unique user profile and source. This article breaks down the most popular dermatologic acids by explaining purposes, type, benefits, risk, and relevant scientific evidence.
1.Alpha Hydroxy Acids (AHAs)
Examples of AHAs include glycolic acid, lactic acid, mandelic acid, and citric acid. All AHAs serve the purposes of exfoliation, brightening, anti-aging, and hydration support. These acids function by dissolving bonds between dead skin cells thus encouraging skin cell turnover and the appearance of smoother skin.
AHAs are derived from various natural sources. Glycolic acid is derived from sugar care, lactic acid from milk, mandelic acid from almonds, and citric acid, of course, from citrus fruits, most commonly oranges and tropical fruits like papayas.
The ideal user of glycolic acid is someone who struggles with oily or sun-damaged skin because it is very effective in reducing fine lines. Lactic acid is geared towards hydration, making it ideal for sensitive or dry skin. Finally, mandelic acid is composed of large-sized molecules which makes it best tolerated by acne-prone skin or darker skin tones.
Studies (Newman 1996. Funaska 2001, and Kornhauser, 2010) show that 5–10% concentrations of glycolic acid improve photoaged skin while lactic acid enhances hydration and firmness.
2. Beta Hydroxy Acids (BHAs)
The leading example of BHAs is the acne holy-grail Salicylic Acid that executes exfoliation internally seeping deep into pores and exercise increased control of oil production. BHAs are oil-soluble meaning that they can penetrate clogged pores in order to dissolve sebum and dead skin thus alleviating some hormonal acne and milia (tiny keratin deposits under the skin).
BHAs were originally derived naturally from willow bark but is now commonly synthesized. As mentioned, BHAs are best for those with bumpy or acne-prone skin.
One clinical study (Liu et al. 2025) confirms that 2% supramolecular salicylic acid gel is effective in treating mild-to-moderate acne as well as removing comedones with overall good tolerability and potential skin barrier improvement. A second, double-blind study (JAAD 2025) suggests that a 2% salicylic acid cleansing formulation yielded a significant reduction in the appearance of acne scars.
3. Polyhydroxy Acids (PHAs)
Two examples of PHAs are gluconolactone and lactobionic acids, which are both synthetic forms of acids naturally found in sugars. These acids are composed of molecules even larger than BHAs, making them the most gentle chemical exfoliator acting slowly and with less irritation.
PHAs are great options for those with sensitive skin, those with rosacea, or those who are simply unable to tolerate strong acids like AHAs and BHAs.
Research evidence (Grimes 2004) indicates that PHAs improve skin texture and hydration while being well tolerated, even for those with atopic dermatitis. High levels of toleration is said to be because of PHA’s humectant and antioxidant properties.
4. Hyaluronic Acid
The fourth acid on our list is the cult classic hyaluronic acid (HA). While HA can be derived from natural sources, it is most commonly produced synthetically via the biofermentation of Streptococcus bacteria. HA works by binding to dihydrogen monoxide molecules up and holding up to 1,000 times its weight in said water therefore helping the skin retain moisture.
HA does not seem to have any serious warnings or restrictions as it’s typically harmless and only serves to pull water into the skin. Arguably, everyone’s skin can benefit from increased hydration. With that said, HA is best for combination or dry and/or aging skin. To most effectively use HA, dermatologist suggest damping the skin with purified water or a facial spray, applying HA, and then applying a water-based moisturizer.
Multiple sets of evidence confirm the effectiveness of topical hyaluronic acid in improving hydration, increasing rejuvenation (Bravo et al. 202), and reducing wrinkle depth by up to 40%.
5. Azelaic Acid
The highly studied Azelaic Acid (AA) is an anti-oxidant, anti-inflammatory, anti-bacterial solution for your skin. Basically, it’s a superfood for your epidermis. Azelaic Acid performs its magic by slowing the production of keratin, preventing clogged pores, inhibiting tyrosinase reducing pigmentation and fighting bacteria, oxidation, and inflammation.
Like AHA and HA, AA can be derived from its natural forms in barley and wheat, but today, it is mostly produced synthetically in order to ensure consistency. AA is best for individuals struggling with milia or those who acne-prone, rosacea-prone, or hyperpigmented skin. In essence, if smooth skin is your goal, consider AA.
AA is one of the most highly studied dermatologic acids. Clinical trials analyzing 15–20% topical AA solutions (Layton 2023, Konisky 2024) produce the conclusion that it is effective for acne vulgaris and rosacea, but with fewer side effects than some prescription treatments like topical vitamin As (Iraji 2007, King 2023). Additionally, weaker AA, when used for prolonged periods, has proven to more effective in reducing the appearance of acne scarring than tretinoin — a gel that is stronger but typically used for a short time (Sauer 2024). Perhaps slow and steady wins this race.
6. Vitamin C (Ascorbic Acid and Derivatives)
L-Absorbic Acid
The pure form of Vitamin C is L-ascorbic acid (LaA). Purse Vitamin C works by neutralizing free radicals caused by UV radiation and pollution. LaA promotes collagen ross-linking, and like AA, inhibits tyrosinase — the enzyme that causes dark spots. In essence, LaA reduces the production of unwanted melanin that leads to hyperpigmentation. LaA is best for oily-to-normal skin and people seeking anti-aging and brightening effects.
LaA is safest in concentrations of 10–20% appearance AND when combined with Vitamin E or Ferulic Acid, which both help stabilize the compound and enhance absorption. Some limitations include that LaC is unstable in light and air because it oxidizes quickly and can irritate sensitive skin. To combat these issues, LaA must be stored in opaque, air-tight packaging.
Evidence from two studies confirm topical LaA reduced wrinkles, hyperpigmentation, and oxidative stress in the skin (Meng et. al. 2013, Nathan 2021)
Vitamin C Derivatives
Because pure Vitamin C is unstable, cosmetic chemists have developed multiple derivatives that are more stable in formulations and gentler on the skin. These compounds convert to LaA once inside the skin. There are six common forms of synthetic, stable, Vitamin C that will be outlined below.
- Magnesium Ascorbyl Phosphate (MAP): MAP is water soluble, gentle, and effective at lower concentrates. It improves hydration and promotes brightening. MAP is safe for sensitive and/or dry skin.
- Sodium Ascobyl Phosphate (SAP): SAP is known for acne-fighting properties and antioxidant effects, often used in formulations for blemish-prone skin.
- Ascorbyl Glucoside (AG): AG is stable and often used in Japanese and Korean skincare to brighten to improve hyperpigmentation
- Tetrahexyldecyl Ascorbate (THD Ascorbate): THD Ascorbate is oil-soluble allowing it to penetrate more deeply into the skin promising collagen stimulation and anti-aging.
- 3-O-Ethyl Ascorbic Acid (3OE): 3OE is a newer derivative with high stability and is showing good results in brightening and reducing hyperpigmentation
No matter skin concerns or type, synthetic vitamin C is recommended for beginners in the skincare world and/or younger individuals who want long-term support without irritation.
An in-depth clinical review (Deeny 2024) and studies (Pullar 2017, Michales2025) show that derivatives are just as effective at delivering the benefits promised from pure Vitamin C but are less potent.
7. Tranexamic Acid (TA)
Last but certainly not least is Tranexamic Acid, or TA. This acid also targets brightness, specially focusing on melasma (unwanted brown/grey patches) treatment. Because of that, TA is best suited for individuals wishing to combat melasma. TA works by inhibiting plasmin which in turn reduces the production of melanin — too much of which is the cause of melasma, along with weakened skin tissues that lead to slowed wound repair.
TA is a synthetic derivative of lysine which is an essential amino acid. A lack of lysine can lead to impaired collagen synthesis and weakened connective tissue thus slowing wound repair and therefore increasing the risk of melasma. TA helps heal wounds, reduce pigments, and strengthen the skin on a structural level.
Evidence points to significant improvements in melasma and other pigmentation disorders following both topical (morning and night) and oral (250mg twice daily) administrations of TA. A second study produced a systematic review of injectable TA.
Conclusion
Whether you’re new to skincare, or a seasoned pro, there is an acid for you! Some more gentle, some more intense; all working for you and your skin! Remember to consult your doctor as always.