AHA vs. BHA: 5 Differences That Decide Which Exfoliant Fits You

AHAs and BHAs are both chemical exfoliants, but they differ in which acids they use, what safety conditions regulators describe, and how strongly sun protection is emphasized. The short answer: AHAs usually mean glycolic or lactic acid with a well-documented sun-sensitivity warning, while BHAs usually mean salicylic acid, which has been claimed to be gentler, though the FDA presents that as a claim rather than its own finding. Here is what the FDA record says.

At a glance: AHA vs. BHA

What the table shows: the two groups share the exfoliant job but carry different documented cautions. AHAs have the more specific sun-sensitivity record, while BHAs carry the more specific "claimed gentler" marketing language that the FDA does not itself endorse.

AHAs: what the FDA record says

The FDA's alpha hydroxy acids page identifies glycolic acid and lactic acid as the predominant AHAs in cosmetic products. The Cosmetic Ingredient Review (CIR) Expert Panel, the industry's safety review body cited by the FDA, concluded that products with glycolic and lactic acid are safe for consumers when three conditions hold. The AHA concentration is 10 percent or less, the finished product has a pH of 3.5 or greater, and the product is formulated to protect against increased sun sensitivity or its directions tell consumers to use daily sun protection.

Sun sensitivity is the central caution. In January 2005 the FDA issued a guidance for industry recommending that AHA cosmetics carry a Sunburn Alert statement. The recommended wording reads: "Sunburn Alert: This product contains an alpha hydroxy acid (AHA) that may increase your skin's sensitivity to the sun and particularly the possibility of sunburn. Use a sunscreen, wear protective clothing, and limit sun exposure while using this product and for a week afterwards."

The FDA's own research, described on the same page, found that after four weeks of AHA use, volunteers' sensitivity to skin reddening produced by UV increased by 18 percent, and sensitivity to UV-induced cellular damage roughly doubled on average. Those effects were reversible: within a week of stopping use, researchers found no significant differences in UV sensitivity.

Adverse reports exist but need context. The FDA page notes 114 reports of adverse reactions to AHA products between 1992 and February 2004, with burning (45 reports) and dermatitis or rash (35 reports) the most frequent. Spontaneous reports like these are not a controlled measure of risk, but they help explain why the labeling guidance exists.

BHAs: what the FDA record says

The FDA lists BHA ingredients as salicylic acid, or related substances such as salicylate, sodium salicylate, and willow extract, plus beta hydroxybutanoic acid, tropic acid, and trethocanic acid. Salicylic acid is the BHA consumers meet most often. The page adds a chemist's footnote worth knowing: from a chemist's perspective salicylic acid is not a true BHA, but cosmetic companies often refer to it as one.

On gentleness, the FDA is careful. Its page says BHAs have been claimed to be effective in reducing the appearance of fine lines and wrinkles, and improving overall skin texture, without the occasional irritation associated with the use of AHAs. That phrasing attributes the claim to others; it is not the FDA's own conclusion.

The CIR panel's 2000 conclusion, as described by the FDA, was that salicylic acid use in cosmetics is safe as used when formulated to avoid irritation and when formulated to avoid increased sun sensitivity. The FDA's practical cautions for BHA products are to patch test before widespread use, follow label directions, avoid use on infants and children, and use sun protection.

Choosing in 3 steps

1. Start from your sun habits and what your skin tolerates. If you spend significant time outdoors, the AHA sun-sensitivity record means daily sunscreen deserves extra attention during use and for a week after stopping. The FDA also advises sun protection with BHA products, so the habit applies either way.
2. Read the label before you buy. For AHAs, look for the concentration and the Sunburn Alert or equivalent sun-protection directions. For BHAs, check the directions for use and any warnings. A product that hides this information is worth skipping.
3. Introduce one exfoliant at a time. Start with the lowest frequency on the label, watch for burning, persistent stinging, or rash, and stop if irritation appears. Avoid layering multiple exfoliating acids while your skin is adjusting.

Keep the evidence level in mind

The FDA pages used here describe ingredients, safety review conclusions, and labeling recommendations. They do not rank one acid as better than the other, so the right choice depends on the product's label and on how your skin responds. The BHA page was last updated on February 25, 2022, and the AHA research and reports it cites are older still, so check the FDA site for newer guidance before relying on any single figure.

Before you buy

Patch test any new exfoliant before applying it widely. Use sunscreen daily while using these products, and reapply as directed on the sunscreen label. Follow the product's directions exactly rather than increasing frequency on your own. The FDA advises against BHA use on infants and children. If you have a skin condition, are pregnant, or take medication that affects your skin, check with a dermatologist or your clinician before starting a chemical exfoliant.

Sources

• FDA, Alpha Hydroxy Acids
• FDA, Beta Hydroxy Acids
• FDA, Guidance for Industry: Labeling for Cosmetics Containing Alpha Hydroxy Acids