Ammonium lactate: what it treats, how to take it, side effects
Last updated September 3, 2026.
Ammonium lactate 12% is a prescription-strength alpha-hydroxy moisturizer for seriously dry, scaly skin. The lactic acid loosens the glued-together dead cells on the surface while the cream base hydrates underneath. Brand names include Lac-Hydrin and AmLactin.
What does it treat?
It treats xerosis (severely dry skin) and ichthyosis vulgaris, an inherited condition that leaves skin fish-scale dry, and it temporarily relieves the itching that comes with both. It is also used off-label for keratosis pilaris, the rough bumps on upper arms and thighs. It manages the dryness; the tendency returns when you stop, so maintenance use is normal.
How do you take it?
Shake the bottle well, apply to the affected areas, and rub in thoroughly, twice daily or as your physician directs. It absorbs best right after bathing. Expect some stinging on cracked or abraded skin; that is the lactic acid, and it fades. One real caution: it makes treated skin more sensitive to sunlight, so protect those areas with clothing and sunscreen. Missed application: apply when remembered unless the next one is near.
Side effects to know
- Common: transient stinging or burning on application (especially on cracked skin), mild redness, itching, and peeling as the scale lifts.
- Serious: allergic reactions are rare; stop and get help for hives, swelling, or blistering. The main cumulative risk is sun sensitivity on treated areas.
Who should not take it?
Do not use it if you have had a hypersensitivity reaction to any ingredient. Keep it off the face unless your doctor says otherwise, and off open wounds. Because it increases sun sensitivity, minimize sun exposure on treated skin and use sunscreen while using it. In pregnancy it is Category B, with animal studies showing no harm at moderate multiples of the human dose, but the decision still belongs with your doctor.
When is it an emergency?
Call 911 for swelling of the face, lips, or throat or trouble breathing after applying. Skin that becomes severely blistered, or a treated area showing spreading redness, pus, or fever, needs same-day care. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why does ammonium lactate sting when I apply it?
Lactic acid is an alpha-hydroxy acid, and it bites on any crack or raw spot in the skin. Stinging that fades within a minute or two is normal and usually lessens as the skin heals over the first weeks. Burning that persists or worsens means the skin barrier is too damaged for it right now; let cracks close first or ask about a gentler start.
Is AmLactin the same as the prescription version?
AmLactin and store-brand 12% ammonium lactate lotions are the same active ingredient at the same strength as the old prescription Lac-Hydrin, now largely over the counter. The label directions are identical: twice daily, rub in well, watch the sun.
Does ammonium lactate help keratosis pilaris?
It is one of the standard choices. The acid loosens the keratin plugs in the follicles on the upper arms and thighs while the base hydrates. Expect smoothing over 4 to 8 weeks of twice-daily use, and expect it to creep back when you stop, so maintenance is the norm.
Why do I need sunscreen with a moisturizer?
Because it is not only a moisturizer. The lactic acid thins the dead outer layer, and the label warns that treated skin burns more easily in the sun. Cover treated areas or use sunscreen while using it and for a period after, especially in summer.
Can I use ammonium lactate on my face?
Not without your doctor's direction. Facial skin is thin, and 12% lactic acid on the face commonly causes significant stinging and irritation. Facial dryness does better with products designed for the face; keep this one for the body.
Is ammonium lactate safe during pregnancy?
It is Category B: animal studies at moderate multiples of the human topical dose showed no harm, but there are no adequate human studies. Most clinicians consider limited body use low risk, yet the call belongs with your obstetric clinician, particularly over large areas.