Last updated: October 2026
Short answer: Both ingredients draw water into skin and loosen rough, built-up skin. Urea is used at 10% or less for dry skin and at much higher strengths for thick, hard skin and nails. Lactic acid is an alpha hydroxy acid; a 12% ammonium lactate lotion is labeled for dry, scaly skin. In one head-to-head study, a 40% urea cream worked faster than 12% ammonium lactate. Both can sting on cracked skin.
At a glance
| Urea | Lactic acid | |
|---|---|---|
| Type | Humectant that also softens thick skin | Alpha hydroxy acid: humectant and gentle exfoliant |
| Typical strengths | 10% or less for dry skin; up to 40% for thick skin and nails | 12% as ammonium lactate; lower in many cosmetic lotions |
| Research | 10% urea reduced water loss in people with atopic skin (skin prone to eczema) | L-lactic acid stimulates how much ceramide (a natural skin fat) skin makes |
| Side effects | Mild irritation; stinging common on eczema-prone skin | Stinging or burning in about 1 in 30 people with dry skin; label advises limiting sun on treated skin |
| On a label | Urea | Lactic Acid, Ammonium Lactate, Sodium Lactate |
What urea does
Urea is part of the skin's own natural moisturizing system, and in creams it does two jobs: it attracts water and it softens thick, rough skin. A review of the clinical literature calls it a potent emollient and keratolytic agent (an ingredient that loosens dead skin). For ordinary dry skin it's typically used at 10% or less. At 40% it's strong enough to soften and lift thickened nails.
A dermatology review notes that 10% urea has been shown to reduce water loss through the skin in people with atopic skin. The main downside is irritation. The urea review found mild irritation was the most common side effect, and stinging and burning were common when it was used on eczema-prone skin.
What lactic acid does
Lactic acid is an alpha hydroxy acid (AHA). It holds water and helps loosen the dead cells that make skin feel rough or bumpy. One form of it, L-lactic acid, also stimulates how skin makes ceramides, which supports the protective layer of natural fats in skin's outer layer.
A 12% ammonium lactate lotion is indicated for dry, scaly skin (xerosis) and ichthyosis vulgaris (an inherited condition that causes very dry, scaly skin). Its label reports stinging and burning in about 1 in 30 people with dry skin, and advises minimizing sun exposure on treated areas.
Head to head: which works better?
In a randomized, double-blind study, 25 people with dry skin each used 40% urea cream on one side of the body and 12% ammonium lactate lotion on the other. By day 14, the urea cream was superior for skin roughness, fissures, thickness and dryness on most measures. It's a small study and compares a very strong urea cream, so it doesn't mean urea beats lactic acid at everyday strengths.
Which should you choose?
- Thick, rough heels, elbows or knees: urea is the usual pick, at higher strengths for small areas.
- Rough, bumpy skin on arms and legs: lactic acid works well, but protect treated skin from the sun.
- Cracked or very sensitive skin: both can sting on broken skin. Start with a plain, fragrance-free cream and add one of these once skin has calmed down.
The American Academy of Dermatology lists lactic acid among the ingredients to look for in a dry-skin cream. If you have painful, bleeding cracks, see a doctor.
How to find them on a label
Urea is simply "Urea." Lactic acid may appear as "Lactic Acid," "Ammonium Lactate" or "Sodium Lactate." Products don't always state the strength on the front, but the ingredient's position tells you a lot. Paste the list into the Ingredient Label Decoder for a rough estimate.
Check your own moisturizer. Paste its ingredient list into our free Ingredient Label Decoder to find the likely 1% line, see a rough percentage for each ingredient, and learn what each one does.
Frequently asked questions
Is urea or lactic acid better for dry skin?
Both work. Urea at 10% or less hydrates dry skin, and higher strengths soften thick skin. Lactic acid hydrates and gently exfoliates. In one small head-to-head study, 40% urea cream improved dry skin faster than 12% ammonium lactate lotion.
Do urea and lactic acid sting?
They can, especially on cracked or eczema-prone skin. The 12% ammonium lactate label reports stinging or burning in about 1 in 30 people with dry skin.
Does lactic acid make skin sensitive to the sun?
The prescribing information for 12% ammonium lactate lotion advises minimizing or avoiding sun exposure on treated skin.
More ingredient comparisons
- Ceramides vs. Hyaluronic Acid: What's the Difference?
- Lotion vs. Cream vs. Ointment: Which Is Best for Dry Skin?
- Glycerin vs. Hyaluronic Acid: Which Humectant Is Better for Dry Skin?
- See all ingredient comparisons
Sources
- Pan M, Heinecke G, Bernardo S, Tsui C, Levitt J. Urea: a comprehensive review of the clinical literature. Dermatology Online Journal. 2013;19(11). https://escholarship.org/content/qt11x463rp/qt11x463rp.pdf
- Purnamawati S, Indrastuti N, Danarti R, Saefudin T. The Role of Moisturizers in Addressing Various Kinds of Dermatitis: A Review. Clinical Medicine & Research. 2017;15(3-4):75-87. https://www.clinmedres.org/content/15/3-4/75
- Ammonium Lactate Lotion, 12%: prescribing information (Drugs.com). https://www.drugs.com/pro/ammonium-lactate.html
- Ademola J, Frazier C, Kim SJ, Theaux C, Saudez X. Clinical evaluation of 40% urea and 12% ammonium lactate in the treatment of xerosis. American Journal of Clinical Dermatology. 2002;3(3):217-222. https://pubmed.ncbi.nlm.nih.gov/11978141/
- American Academy of Dermatology. Dermatologists' top tips for relieving dry skin. https://www.aad.org/public/everyday-care/skin-care-basics/dry/dermatologists-tips-relieve-dry-skin
About this page
We wrote this comparison from the sources listed above and confirmed each figure on the linked page in October 2026. It is general information, not medical advice. If you have painful, cracked, bleeding or persistent skin problems, see a doctor or dermatologist.
Corium 21 is a family-owned company that makes a moisturizing cream with certified organic aloe vera. Trusted since 1994. Family-owned in Oregon. It is a cosmetic moisturizer: it moisturizes and helps relieve dryness. It is not intended to diagnose, treat, cure, or prevent any disease.