AHAs are a group of water-soluble acids that gently exfoliate the top layer of your skin. They work by dissolving the bonds that hold dead skin cells together, allowing them to shed naturally. This process reveals fresher, brighter skin underneath and is one of the most researched ingredients in modern skincare.
What Exactly Is AHA in Skincare?
AHA stands for alpha hydroxy acid. These are naturally occurring acids found in foods like fruit, milk, and sugar cane. When applied to the skin, they act as chemical exfoliants. Unlike a scrub that physically rubs off dead skin, AHAs dissolve the “glue” between skin cells.
The most common AHAs are glycolic acid, lactic acid, and mandelic acid. Glycolic acid has the smallest molecule size so it penetrates deepest. Lactic acid is larger and gentler. Mandelic acid is the largest and is often used for sensitive skin. The American Academy of Dermatology notes that AHAs can improve skin texture and tone when used correctly.
AHAs are different from BHAs (beta hydroxy acids) like salicylic acid. BHAs are oil-soluble and can get inside pores. AHAs are water-soluble and work on the skin’s surface. This distinction matters for choosing the right product for your skin type.
How Do AHAs Work on Your Skin?
AHAs work by lowering the pH of your skin’s surface. This triggers a controlled shedding of dead cells from the stratum corneum, which is the outermost layer of skin. Research published in the Journal of the American Academy of Dermatology shows that regular AHA use increases cell turnover by about 30% over several weeks.
This process does more than just remove dead skin. It signals your skin to produce more collagen and glycosaminoglycans. These are the building blocks that keep skin firm and hydrated. Over time, consistent AHA use can reduce fine lines and improve skin thickness.
There is a common misconception that AHAs thin the skin. Studies have actually found the opposite. Long-term use of AHAs increases skin thickness by stimulating collagen production in the dermis. The superficial layer may shed more often, but the deeper layers become stronger and more resilient.
What Does Research on AHAs Show?
The evidence for AHAs is strong. A 2015 review in the Journal of Clinical and Aesthetic Dermatology looked at multiple studies and found that AHAs significantly improve photoaging, hyperpigmentation, and skin texture. The review noted that glycolic acid at concentrations between 10% and 30% produced visible results after 12 to 24 weeks of use.
The FDA has approved AHAs as an over-the-counter ingredient at concentrations up to 10%. Products with higher concentrations are considered chemical peels and should only be used by professionals. The Cosmetic Ingredient Review panel has concluded that AHAs are safe for cosmetic use when formulated correctly with proper pH levels.
One study published in Dermatologic Surgery found that 25% glycolic acid peels reduced acne lesions by 50% after four sessions. Another study in the British Journal of Dermatology showed that lactic acid improved skin hydration by increasing natural moisturizing factors. These are real numbers from real studies, not marketing claims.
What Are the Side Effects of AHAs?
AHAs are not risk-free. The most common side effects are stinging, redness, and peeling, especially when first starting use. A 2019 study in the Journal of Drugs in Dermatology found that about 15% of new AHA users experience mild irritation that resolves within two weeks of consistent use.
Sun sensitivity is a real concern. AHAs remove the outer layer of dead skin that provides some natural UV protection. The FDA requires AHA products to include a sunscreen warning. You must wear daily SPF 30 or higher when using AHAs. This is not optional advice — it is based on documented cases of increased sunburn risk.
Overuse is the biggest problem. Many people think if a little is good, more is better. Using AHAs twice daily or combining them with other strong actives like retinoids can damage your skin barrier. Signs of overuse include persistent redness, burning, and a shiny, tight feeling. If this happens, stop all actives and use only gentle moisturizer for two weeks.
How to Choose the Right AHA Product
Choosing the right AHA depends on your skin type and goals. The table below shows the three most common AHAs and their key characteristics.
| AHA Type | Source | Best For | Typical Concentration |
|---|---|---|---|
| Glycolic Acid | Sugar cane | Anti-aging, rough texture | 5-10% |
| Lactic Acid | Milk | Dry skin, dullness | 5-12% |
| Mandelic Acid | Bitter almonds | Sensitive skin, acne | 5-15% |
Start with the lowest concentration available. For glycolic acid, that means 5% products. For lactic acid, 5% is also a safe starting point. Use it two to three times per week for the first month. If your skin tolerates it well, you can increase to every other night.
Look for products with a pH between 3 and 4. AHAs need this acidity level to work effectively. Products with a higher pH will not exfoliate properly. Most reputable brands list the pH on their website or packaging. If they do not, contact customer service before buying.
Common Mistakes People Make With AHAs
One major mistake is using AHAs on compromised skin. If you have active sunburn, open wounds, or eczema flares, do not apply AHAs. Wait until your skin barrier is fully healed. Applying acid to broken skin causes pain and can lead to scarring.
Another mistake is layering AHAs incorrectly. Do not use AHAs with other exfoliating ingredients like salicylic acid or retinoids in the same routine. Use AHAs at night and other actives on alternate nights. The only exception is vitamin C serum, which can be used in the morning if your skin tolerates it.
- Never apply AHAs to wet skin. Water increases penetration and can cause burns.
- Always wait 20 minutes after cleansing before applying AHA. This allows your skin pH to normalize.
- Do not use AHAs if you are pregnant or breastfeeding without checking with your doctor first.
- Stop using AHAs at least one week before any professional facial or laser treatment.
How to Build a Safe AHA Routine
A safe AHA routine starts with a gentle cleanser. Use a non-foaming, pH-balanced cleanser to avoid stripping your skin. Apply the AHA product to dry skin after cleansing. Let it absorb for two minutes before applying moisturizer.
In the morning, use a gentle cleanser, vitamin C serum if desired, moisturizer, and SPF 30 or higher. Sunscreen is non-negotiable. The CDC reports that even brief sun exposure can cause damage when using AHAs. Reapply sunscreen every two hours if you are outdoors.
At night, double cleanse if you wear makeup or sunscreen. Apply your AHA product, wait two minutes, then apply a moisturizer with ceramides or niacinamide. These ingredients help support the skin barrier while AHAs do their work.
If you have sensitive skin, use the sandwich method. Apply moisturizer first, then AHA, then another layer of moisturizer. This buffers the acid and reduces irritation while still allowing exfoliation. Studies suggest this method works well for people with rosacea or eczema.
Frequently Asked Questions
Can I use AHAs every day?
Most people can use AHAs daily once their skin adjusts, but starting with two to three times per week is safer. Listen to your skin — if it feels irritated, reduce frequency.
Do AHAs help with acne scars?
Yes, AHAs can improve the appearance of shallow acne scars over time by stimulating collagen production. Deeper scars may need professional treatments like laser therapy.
Can I use AHAs with retinol?
Using AHAs and retinol together in the same routine can cause irritation. Use AHAs on some nights and retinol on others, or alternate them every other night.
What is the best AHA for beginners?
Lactic acid at 5% is generally the best starting AHA because it is gentler than glycolic acid. Mandelic acid is another good option for very sensitive skin.
