Ingredient

Ammonium Lactate

Lactic acid, buffered so it stings less. The 12% lotion is the standard first move for very dry, scaly skin and for keratosis pilaris.
At a Glance

Ammonium lactate is lactic acid partly neutralised with ammonium hydroxide, which raises the pH and makes it much easier to tolerate than plain lactic acid. It does two things at once — pulls water into the skin and loosens the scale on the surface — which is why 12% lotion is the most-recommended product for keratosis pilaris and for rough, scaly legs and arms. It is cheap and widely available. The catches are that it stings on broken or freshly shaved skin, and that it increases sun sensitivity, so any treated skin that sees daylight needs sunscreen.

Key Facts

What It IsLactic acid buffered with ammonium hydroxide — a humectant and a mild exfoliant in one
Best ForKeratosis pilaris, dry scaly legs and arms, rough elbows and heels, thickened or scaly skin
Typical Strength12% over the counter (AmLactin, Lac-Hydrin and generics). 5–6% versions exist and are much weaker
Rx RequiredNo. The 12% strength has been over the counter in the US for years
Cost$12–$25 for a large bottle. Store-brand 12% lotions are the same strength and work the same

How It Works

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Lactic acid is an alpha hydroxy acid, and it does two separate jobs on skin. First, it is a humectant — it holds water in the surface layer, and it occurs naturally in skin as part of what is called natural moisturizing factor, the mix of small molecules that keeps the outer layer flexible. Second, at higher concentrations it breaks the bonds between dead surface cells so they shed instead of building up as scale. That combination is unusual: most exfoliants dry the skin while they exfoliate it.

The ammonium part is what makes it usable over large areas. Plain 12% lactic acid is acidic enough to sting sharply. Partly neutralising it with ammonium hydroxide raises the pH to around 4.4 to 5.5, which takes most of the sting out while keeping most of the effect. It is the same active doing the same thing with the edge taken off — which is why ammonium lactate can go on both legs daily and undiluted lactic acid cannot.

What It Treats

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Strong evidence
In keratosis pilaris, ammonium lactate loosens the keratin plug while treating the dryness underneath. It is usually the first thing tried.
Limited evidence
Applied to seborrheic keratoses to soften the thickened surface. It improves texture only — the growth stays and returns to its previous appearance when stopped.
Strong evidence
Ammonium lactate has good trial data in dry, scaly skin, and it is one of the few over-the-counter options that both hydrates and exfoliates without a scrub.

How to Use It

Where it fits
  • This is a leave-on body lotion, applied after showering while the skin is still slightly damp. Once or twice daily. Do not rinse it off, and do not use it as a wash.
Start slowly
  • Every other day for the first week if your skin is sensitive, then daily. A few days of stinging on rough or cracked skin is normal and usually settles.
  • If it stings badly rather than tingles, the skin underneath is more broken than you thought. Use a plain moisturizer for a few days and start again after.
Shaving
  • Do not apply it straight after shaving or waxing. Wait a day. This is the most common complaint about it and it is entirely avoidable — apply it in the evening on days you shave in the morning, or the other way round.

Pairing & Conflicts

What to pair it with

Sunscreen on any treated area that sees daylight. This is a genuine pairing rather than boilerplate — the extra sun sensitivity is real and lasts about a week past your last application.

A plain occlusive moisturizer or ceramide cream over the top on very dry skin. Ammonium lactate pulls water in, and something greasy on top keeps it there.

A gentle shower routine — a soft cloth, not a scrub. Physical scrubbing on skin that is already being chemically exfoliated is how people end up irritated.

Urea, on alternate days. Both loosen scale by different routes, and if one has failed the other is a fair next try. Layering them at full strength is unnecessary.

What not to mix

Retinoids on the same area at the same time. Both exfoliate, and the sum is more irritation than benefit. Alternate nights if you use a body retinoid.

Benzoyl peroxide or salicylic acid on the same patch at the same time, for the same reason.

Freshly shaved or waxed skin. Wait a day.

Broken, cracked, weeping or actively inflamed skin. It will sting hard and it does nothing useful on skin that is not intact.

The face. Twelve percent is formulated for body skin and is stronger than most faces want, and it should stay well away from the eyes.

Side Effects

Nearly everything here is local irritation, and nearly all of it is managed by adjusting how often you use it.

Common and expected
  • Stinging or burning for a few minutes after applying, worse on rough or cracked skin and worse in the first week.Redness. Increased sun sensitivity — sunburn happens faster on treated skin. Dryness or peeling if you go daily too soon. A sharp sting on freshly shaved skin, which is entirely predictable and entirely avoidable.
Tell your doctor
  • Stinging that has not settled after two weeks, or that is getting worse.A rash that spreads beyond where you applied it, or that itches and blisters. That pattern suggests allergy rather than irritation. Dark patches appearing on treated areas after sun exposure. That is post-inflammatory pigmentation, it is more common and more persistent on brown and Black skin, and it is worth stopping and getting advice before restarting. No change in scale or bumps after eight weeks of daily use.
Stop and get care
  • Skin that becomes raw, weeping or eroded.Blistering. Spreading redness, warmth, swelling or pus, which suggests infection. Widespread hives or swelling of the face or lips after use, which is rare.

Who Should Avoid It

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Do not start it on skin that is broken, cracked, weeping or actively inflamed. Settle that first — the sting is severe and it does nothing useful on skin that is not intact.

Do not use it on infants and young children without a doctor's direction.

Do not use 12% on the face. It is a body product, and there are gentler options for facial skin.

Do not use it on anyone who cannot avoid sun on the treated area and will not use sunscreen. That is not a soft recommendation — the photosensitivity is real, it lasts about a week past the last application, and on brown and Black skin the consequence is dark patches that take months to fade.

Avoid it if you have reacted to lactic acid or another alpha hydroxy acid product before.

Pregnancy and breastfeeding: topical lactic acid is generally considered acceptable and very little is absorbed. There is no restriction on it.

Otherwise there is no group who has to avoid it.

How Long Until It Works

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Day one. Skin feels softer and less tight straight away. That is the humectant half working, and it happens at any strength.

Two weeks. Roughness starts to reduce. Keratosis pilaris bumps feel smoother to the hand before they look different in the mirror.

Four to six weeks. The honest point to judge it, and where the trials measured. Expect noticeably smoother, less scaly legs and arms, and a real reduction in the roughness of keratosis pilaris.

Eight weeks. About as good as it gets. If nothing has changed, the answer is a different ingredient rather than more of this one.

What it will not do. It does not clear keratosis pilaris. The bumps get smaller and much smoother, and most people still have some. It also does very little for the redness around each bump, which is often what people actually dislike. Anyone selling you a cure for keratosis pilaris is overselling — there is not one.

When you stop. Roughness returns over four to eight weeks. This is maintenance, not repair. Most people who do well on it drop to a few times a week rather than stopping.

FAQ+
Is ammonium lactate the same as lactic acid?It is lactic acid partly neutralised with ammonium hydroxide, which raises the pH and makes it far less stinging. Same active, gentler delivery, which is why it can be used daily over large areas.
Is AmLactin the same as the store brand?If both say 12% ammonium lactate, yes. The active and the strength are identical. Differences in feel come from the base, not the medicine.
Will it get rid of my keratosis pilaris?No, and nothing does. It makes the bumps smaller and much smoother, which is a real improvement, and most people still have some. It does little for the redness around them.
Why does it sting after I shave?Because shaving takes off the top layer of skin, and an acid on freshly abraded skin stings. Put it on a different schedule from shaving — evening application when you shave in the morning, or the reverse.
Do I need sunscreen with it?On any treated area that sees daylight, yes. Alpha hydroxy acids increase sun sensitivity and the effect lasts about a week past your last application. Applying at night is the easy workaround for skin that stays covered.
Can I use it on my face?Twelve percent is formulated for body skin and is stronger than most faces need. There are better-tolerated facial options.
Ammonium lactate or urea?Both work for the same problems and neither is clearly better. Ammonium lactate has more trial evidence in keratosis pilaris. Urea is less likely to sting on freshly shaved skin and comes in stronger versions for very thick scale. If one has not worked after six weeks, try the other rather than going stronger.
Is 5% enough?Usually not, if what you want is less scale. The 5% and 6% versions hydrate but do very little exfoliating. Twelve percent is the strength the evidence sits behind.
Can I use it on my child's keratosis pilaris?Ask first. It is often used in older children, but it stings, and a small child will simply refuse it rather than explain why. Start with a plain moisturizer.
Does it help with dark marks?Only indirectly, by turning the surface layer over a little faster. It is not a pigment treatment, and used without sunscreen it can make pigmentation worse rather than better.