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What Are AHAs? Alpha-Hydroxy Acids for Skin

Alpha-hydroxy acids (AHAs) are a group of water-soluble acids, often derived from fruit or milk, used in skincare to exfoliate the skin’s surface. They help loosen the bonds between dead skin cells to reveal smoother, brighter skin.

At a glance

Term
AHA
What it is
Chemical exfoliant ingredient
Also called
alpha-hydroxy acid
In one line
AHAs are skincare acids that gently dissolve the ‘glue’ holding dead skin cells to the surface, making your skin look brighter and feel smoother.

What AHA means

AHA stands for alpha-hydroxy acid, a class of chemical compounds used widely in skincare. Common AHAs include glycolic acid (from sugar cane), lactic acid (from milk), and citric acid (from citrus fruits). Because they are water-soluble, AHAs work on the surface of the skin. Their main job is to provide chemical exfoliation, helping to speed up cell turnover. This can improve the appearance of skin texture, reduce the look of fine lines, and create a more even skin tone.

AHAs work by weakening the bonds that hold dead skin cells together on the top layer of the skin. Think of it as dissolving the glue between old skin cells so they can be shed more easily. Our skin naturally sheds these cells, but this process can slow down due to age or sun damage, leading to a dull or rough appearance. By promoting this shedding process, AHAs help reveal the newer, more radiant skin cells underneath.

You can find AHAs in many types of skincare products, including cleansers, toners, serums, and masks, at various concentrations. Different AHAs have different properties. For example, glycolic acid has the smallest molecule size, allowing it to penetrate effectively, while lactic acid has a larger molecule and is also known for its hydrating properties. When first introducing AHAs, it’s usually best to start with a product that has a low concentration and use it only a few times per week.

While effective, AHAs have limitations and require careful use. They increase the skin’s sensitivity to the sun, making daily sunscreen use essential to prevent sun damage. Overuse or using a concentration that is too high for your skin can lead to irritation, redness, dryness, and a compromised skin barrier. They are not a one-size-fits-all solution and may not be suitable for very sensitive skin or certain skin conditions like rosacea.

What public guidance says

The American Academy of Dermatology recommends using a broad-spectrum, water-resistant sunscreen with an SPF of 30 or higher. This is critical when using AHAs, as they make your skin more sensitive to the sun.

How to use AHAs

  1. Start with a product that has a low concentration and use it just a few times a week to see how your skin responds.
  2. Apply AHAs at night to clean, dry skin. This minimizes sun sensitivity and allows the product to work without interference.
  3. Follow up with a simple, gentle moisturizer to help hydrate your skin and support its natural barrier.
  4. Always wear a broad-spectrum sunscreen with an SPF of 30 or higher during the day, as AHAs make your skin more vulnerable to sun damage.
  5. Avoid using other strong active ingredients, like retinol or another exfoliant, in the same routine to reduce the risk of irritation.

AHA vs. similar terms

Compared with How AHA differs What the other term means
BHA AHAs are water-soluble and work on the skin’s surface, making them ideal for addressing concerns like dullness and uneven texture. BHAs (beta-hydroxy acids) are oil-soluble, which allows them to penetrate into pores to clear out excess oil and dead skin.

Common misconceptions

  • Myth: A higher percentage works better and faster. Higher concentrations increase the risk of irritation and damaging your skin barrier. Consistent use of a lower, well-tolerated percentage is often more effective and sustainable.
  • Myth: You need to feel a sting for it to be working. While very mild, brief tingling can occur, significant stinging or burning is a sign of irritation, not effectiveness. Skincare should not be painful.
  • Myth: AHAs thin your skin over time. AHAs exfoliate the outermost layer of dead skin, but they can also help stimulate collagen production deeper in the skin, which contributes to its firmness and thickness.

Related terms

When to bring in a professional

Consult a board-certified dermatologist if you experience persistent irritation or have questions about incorporating AHAs into your routine.

  • Persistent redness, peeling, or a burning sensation that doesn’t go away.
  • A sudden increase in breakouts or skin sensitivity after starting an AHA product.
  • Worsening of a skin condition like eczema or rosacea.
  • If you are unsure which type of exfoliant is right for your skin type and concerns.

How this entry was made: drafted with AI assistance from general, widely published definitions, checked in a separate verification pass for invented numbers and claims, and edited by the Millennials Wellness editors. General information only, not medical, financial or legal advice. Last checked October 2026. Our ground rules · Back to the glossary