AHA stands for alpha-hydroxy acid, and BHA stands for beta-hydroxy acid. AHA and BHA are hydroxy acids that people use to treat skin conditions such as acne. AHAs and BHAs both work as exfoliants, but they work in different ways.

The most common hydroxy acids include glycolic acid, lactic acid, and salicylic acid.

People can find these ingredients in a variety of cosmetic products claiming to treat different skin conditions and improve skin features.

Choosing the most appropriate product to get a specific result can be challenging.

This article explores the differences between AHA and BHA, which conditions they treat, and how best to use them.

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AHAs include five naturally occurring organic acids:

  • glycolic acid
  • citric acid
  • malic acid
  • tartaric acid
  • lactic acid

These are weak acids that may improve the appearance of the skin. People can find AHAs in the form of skin peels to treat:

  • acne
  • scars
  • melasma (brown or gray patches of skin)
  • hyperpigmentation (patches of darker skin)
  • roughness
  • age spots
  • seborrhea (rash with red and itchy spots and white scales)

People use BHAs to reduce the appearance of wrinkles and fine lines on the skin and improve the skin’s overall texture.

Salicylic acid, which is a type of BHA, is a common ingredient in acne products.

Different BHAs include:

  • salicylic acid
  • beta-hydroxybutanoic acid
  • tropic acid
  • trethocanic acid

The most used hydroxy acids are glycolic acid, lactic acid, and salicylic acid.

One of the most common benefits of hydroxy acids is their ability to improve sun-damaged skin.

To measure improvements in sun-damaged skin, doctors check skin roughness, changes in skin color, and collagen density.

Because of the reported benefits of hydroxy acids, many skin care companies have developed cosmetic products that include them.

AHAs and BHAs both work as exfoliants, but they work in different ways.

AHAs work by reducing the concentration of calcium ions in the skin. This promotes the shedding of skin cells at the surface.

BHAs are also a skin peeling agent, but salicylic acid has additional antibacterial actions.

Despite the many studies on AHAs and BHAs, experts still lack adequate information on their safety and efficacy.

Studies typically use products with different active ingredients and different instructions for use, making comparing products a challenge.

Many products with hydroxy acids are exfoliants and moisturizers.

People can also find them in low concentrations in over-the-counter prescription creams and lotions.

People can find hydroxy acids in higher concentrations in chemical peels used for treating calluses, acne, photoaging, skin growths, and psoriasis.

AHAs and BHAs are both exfoliants, but each hydroxy acid has other properties that make it more appropriate for treating certain skin conditions or improving certain skin features.

Compared with the AHA glycolic acid, salicylic acid causes less irritation.

Another difference between AHAs and BHAs is that BHAs increase the skin’s resistance to ultraviolet skin damage and also have antibacterial effects.

The antibacterial effects of BHAs make them appropriate ingredients for acne products.

AHAs provide more aggressive exfoliation, which may be more appropriate for repairing sun-damaged skin and improving the effects of aging.

They also have effects on collagen and procollagen production. These are substances that can improve the appearance of photoaged skin.

Since AHAs are more aggressive, their use requires caution because of the potential for sun sensitivity.

A person should base their choice of skin product on which hydroxy acid is most suitable for their specific need.

BHA seems to be more effective for treating skin conditions like acne because of its antibacterial properties.

AHAs, such as glycolic and lactic acid, may be effective in treating changes in skin color such as melasma, solar lentigines, and post-inflammatory hyperpigmentation. Experts believe that the quicker action of AHA makes it a better option for improving skin color than BHA-containing products.

Also, because of AHA’s more aggressive mechanism of action and its effects on collagen, people looking to improve sun-damaged or aged skin might prefer AHA-containing products. Lactic acid, another AHA, is an excellent moisturizer.

However, it is worth noting that much of the existing research appears gathered from studies whose participants had lighter skin tones. The safety and effectiveness of these products in populations with darker skin tones requires further study.

Products that contain AHAs report several benefits, such as:

  • smoothing fine lines and surface wrinkles
  • improving skin texture and tone
  • unblocking and cleansing pores
  • improving skin appearance in general

AHAs work by exfoliating the skin. Exfoliation sheds surface skin cells. How much a product with AHAs exfoliates the skin depends on the concentration of the AHA ingredient, its acidity, and other ingredients found in it.

Side effects

Using AHAs comes with certain side effects. Most often, these side effects occur in skin peeling products. Side effects are local, meaning they affect the area of skin where the product was applied. They may include:

  • burning sensation on the skin
  • rash
  • swelling
  • changes in skin color
  • blisters or welts
  • skin peeling
  • itching
  • skin irritation
  • chemical burns
  • increased risk of sunburn

To use skin products containing AHA safely, follow the directions on the product’s label carefully. Be aware of any warnings on the product label.

People who use products containing AHA should regularly use sun protection. Sun protection includes wearing sunscreen, wearing protective clothing, and limiting sun exposure.

The Cosmetic Ingredient Review (CIR) Expert Panel suggests that products containing glycolic acid and lactic acid are safe if:

  • The concentration of AHA is 10% or less.
  • They have a pH of above 3.5.
  • The product protects the skin from increased sun sensitivity, or the package recommends daily sun protection.

Before choosing a product with AHA, people should speak with a doctor or dermatologist to ensure the product will be safe and effective.

According to the CIR Expert Panel, products containing BHA, such as salicylic acid, are safe if their formulation was designed to avoid both skin irritation and increased sun sensitivity.

If the producer of the skin care product expects that the user may experience sun sensitivity after applying their product, there must be warnings clearly displayed on the product packaging.


The Food and Drug Administration (FDA) recommends certain precautions when using products that contain BHA. These precautions include:

  • testing products that contain BHA on a small area of the skin before applying to a larger surface of the skin
  • following the instructions on the product label closely
  • avoiding exceeding the recommended applications
  • avoiding using BHA-containing skin products on infants and children
  • practicing sun protection when using BHA-containing products

Before using a product with BHA, people should speak with a doctor or dermatologist to find the safest and most effective product.

Since both AHAs and BHAs are exfoliants, they can be very irritating to the skin if combined.

If a person wants to use both AHA and BHA products for different skin problems, they should consult a doctor. Excessive skin irritation may worsen skin conditions and appearance.

Some types of AHA are less aggressive and may be more appropriate to combine with BHA.

Products that contain hydroxy acids may also not require daily use, which can help with skin irritation if people need more than one product.

Spot treating the skin with different products may also help prevent irritation to the entire skin. For example, a person can try applying an anti-aging or sun damage repair product on their entire face, but spot-treat areas of the skin with acne with a BHA-containing product.

Many skin care companies add hydroxy acid ingredients to their products because of their reported benefits.

AHA and BHA both exfoliate the skin.

AHA seems to be more effective for treating issues with skin pigmentation.

BHA is less aggressive and irritating and has additional antibacterial properties.

Both AHA and BHA repair sun-damaged skin.

To choose the most appropriate product, people should speak with a doctor or dermatologist who can help diagnose skin conditions and recommend the safest and most effective product.