The Ordinary Lactic Acid Review: 10% + HA vs 5%, Tingling and How Often to Use It

The Ordinary Lactic Acid 10% + HA is a cheap, well-formulated AHA serum for dull, rough skin, best used a few evenings a week rather than every night at first. At about pH 3.8 it tingles for many people, which is expected. Start with the 5% version if your skin is dry, reactive or new to acids, and never use it on the same night as a retinoid.

If you want to check its ingredient list against your own skin type before buying, you can scan the barcode or photograph the label with the ingredient scanner in Pori.

Below we look at what's in the bottle, how the 5% and 10% versions differ, why it tingles, how often to use it, and how to combine it with retinoids without irritating your skin. This is an ingredient-and-evidence review based on The Ordinary's published information and the dermatology literature, not a hands-on test.

What is The Ordinary Lactic Acid 10% + HA?

It's a water-based exfoliating serum with 10% lactic acid, a crosslinked hyaluronic acid and a soothing plant extract. The Ordinary calls it "a high-strength exfoliator that works to reveal smoother skin" and says it targets textural irregularities, dullness and uneven tone.

The ingredient list is short: water, lactic acid, glycerin, a few glycols, sodium hydroxide to set the pH, the HA crosspolymer, the pepperberry extract, two gums and preservatives. There's no fragrance and no essential oil, which keeps the irritation load down to the acid itself.

What does lactic acid do for dull and rough skin?

Lactic acid loosens the bonds between dead cells on the surface so they shed more evenly, which makes skin look smoother and reflect light better. It's one of the two most common AHAs in cosmetics; the FDA notes that glycolic acid and lactic acid lead the category. A review of hydroxy acids in Clinical, Cosmetic and Investigational Dermatology describes lactic acid as used in various topical formulations to exfoliate the skin, and lab work it summarizes found lactic and glycolic acid can directly inhibit tyrosinase, the enzyme behind melanin.

Lactic acid also attracts water. DermNet lists alpha hydroxy acids such as lactic acid among humectants that attract and retain water in the outer skin layer, which is one reason it's often recommended for dry skin over glycolic acid. Our explainer on lactic acid for dry and dull skin goes further into that comparison, and why skin looks dull covers the other causes worth ruling out first, from dehydration to poor sleep.

Lactic Acid 5% vs 10%: which should you choose?

Choose 5% if you're new to acids, have dry or easily irritated skin, or plan to use it alongside a retinoid on other nights; choose 10% if you've used acids before and want a stronger effect. The two share the same base, pH and directions. The Ordinary describes the 5% as "a milder exfoliator" and calls it ideal for dry and sensitive skin, though both product pages also say not to use them on sensitive, peeling or compromised skin.

The 10% sits right at the safety line regulators use. The FDA summarizes the Cosmetic Ingredient Review panel's conclusion that lactic and glycolic acid products are safe for consumers when the AHA concentration is 10 percent or less and the pH is 3.5 or higher, with directions to use sun protection. The Ordinary's 10% formula meets both limits, with a pH just above the floor, so it's a full-strength consumer product. If you're unsure, the price difference is about a dollar, and moving from 5% to 10% later is easy.

Why does The Ordinary Lactic Acid tingle?

The tingle comes from applying an acid at a low pH; a mild, brief sting that fades within a few minutes is common, while burning that lingers is a signal to stop. The Ordinary sets the pH near 3.8 on purpose: its page says lactic acid's pKa is 3.8, and that with the pH this close to it there is "an optimal balance between salt and acidity". The same acidity that makes it work is what you feel.

DermNet notes that how much any chemical exfoliant stings depends on the chemical, its concentration and individual factors. Damp skin, freshly shaved skin and skin that's already irritated sting more. A few ways to soften it:

• Apply to completely dry skin, a few minutes after cleansing.
• Dilute it, which The Ordinary allows: mix a drop or two into a plain moisturizer until your skin adjusts.
• Keep it away from the eye contour and the corners of the nose and mouth.
• Skip it on nights your skin already feels tight, sunburned or raw.

Rinse it off and stop if you get redness that lasts, burning, itching, blistering or swelling. The Ordinary's warning covers the same signs and advises seeing a physician if irritation occurs.

How often should you use The Ordinary Lactic Acid?

Start two or three evenings a week and increase only if your skin stays comfortable; The Ordinary's maximum is once daily, ideally in the evening. Most people with dull or rough skin don't need it every night. The brand also asks you to limit how often and how long the product stays in contact with skin, which is a clear hint to build up slowly.

1. Weeks 1 to 2: two evenings a week, after cleansing and before moisturizer.
2. Weeks 3 to 4: three evenings a week if there's no lasting redness or peeling.
3. After a month: stay at three, or try every other night. Daily use suits only very resilient skin.

Back off if you see shiny, tight or flaky patches, which are signs of over-exfoliation. Our chart on how often to exfoliate your face breaks this down by skin type.

Do you need sunscreen with lactic acid?

Yes. AHAs increase your skin's sensitivity to UV, and the FDA reports a four-week study in which volunteers' sensitivity to UV-induced reddening rose 18 percent, an effect that reversed after they stopped. The FDA's recommended "Sunburn Alert" tells users to wear sunscreen, cover up and limit sun exposure while using an AHA and for a week afterward. The Ordinary prints the same warning on both versions. Use a broad-spectrum SPF every morning, even though you apply the acid at night.

Can you use The Ordinary Lactic Acid with retinol or tretinoin?

Yes, but on different nights, not layered together. The Ordinary lists retinoids among the products not to use with its lactic acid serums, along with other direct acids, direct vitamin C, peptides and copper peptides. Both ingredients can cause dryness and irritation; DermNet lists retinoid dermatitis, with redness, peeling and dry skin, as a side effect of topical retinoids.

The AAD's dermatologists advise starting a retinoid with the least intense formula every other night, slowly building up, and using moisturizer to limit irritation. That leaves room for an alternating schedule:

• Night 1: lactic acid, then moisturizer.
• Night 2: retinoid, then moisturizer.
• Nights 3 and 4: moisturizer only, to let the barrier recover.

That's the logic behind skin cycling. If you're on a prescription retinoid such as tretinoin, ask your prescriber before adding any acid, since DermNet ranks tretinoin as the most irritating of the topical retinoids. DermNet also notes that retinoids increase sun sensitivity, so pairing the two makes daily sunscreen even more important.

Two other cautions: the AAD says retinoids should not be used during pregnancy, and anyone with eczema, rosacea or a damaged barrier should ask a dermatologist before starting either ingredient.

Lactic acid or glycolic acid?

For dry or first-time users, lactic acid is a reasonable place to start, and The Ordinary positions both of its lactic serums for dry skin. Both acids fall under the same 10% and pH 3.5 consumer guidance from the FDA's summary, and both exfoliate the surface; lactic acid also counts as a humectant in DermNet's list, which is a useful extra for skin that runs dry. If clogged pores and blackheads are your main concern, an oil-soluble BHA usually suits better; our AHA vs BHA guide lays out the choice.

Who should skip it?

Skip it, or ask a dermatologist first, if your skin is currently peeling, sunburned, broken or reactive. The Ordinary says not to use either version on sensitive, peeling or compromised skin. People with rosacea or active eczema on the face should also be cautious with any acid. If you're pregnant or breastfeeding, the product pages don't address it, so check with your doctor before adding a leave-on acid.

The verdict

The Ordinary Lactic Acid 10% + HA does what a lactic acid serum should, at a price that's hard to beat: a regulation-strength AHA at a pH that lets it work, a minimal formula with no fragrance, and honest warnings on the page. The tingle is part of the deal, and the risk comes from overusing it. Start with the 5% if you're unsure, keep it to a few nights a week, never stack it with a retinoid on the same night, and wear sunscreen every morning.