Urea in skin care: the humble moisturizer that also smooths

Urea doesn’t have the glamour of newer ingredients, and its name doesn’t help. But it’s one of the most studied moisturizing ingredients there is, and it does something few others do: depending on the strength, it can hydrate skin, smooth it, or both. Here’s how it works, what the evidence says and where it can sting.

What urea is and why your skin already has it

Urea is a small molecule that attracts and holds water. Your body makes it, and your skin uses it. A 2021 review in Dermatology and Therapy describes urea as part of the natural moisturizing factor, the mix of water-holding substances inside the outer layer of your skin, and says it’s essential for keeping that layer hydrated and intact.

Because urea dissolves easily in water, it’s simple to add to lotions and creams, which is one reason it has been used in dermatology for so long.

In skin care, urea works in two ways:

• As a humectant, an ingredient that draws water into the outer skin and helps keep it there.
• As a keratolytic, an ingredient that loosens and softens the thick, scaly buildup of dead cells.

DermNet lists urea alongside glycerin and alpha hydroxy acids in the humectant group and notes the same descaling effect.

Low vs high strength: what the percentages mean

The strength on the label changes what urea mainly does. The 2021 review groups it like this:

• Low (about 2 to 10 percent): mainly moisturizing and supporting the skin barrier, the outer layer that keeps water in and irritants out. Good for everyday dry skin.
• Medium (about 10 to 30 percent): moisturizing plus softening of rough, scaly skin.
• High (30 percent and up): mainly softening very thick skin, such as calluses, and used in some medical treatments, including for nails.

The review also describes lab work showing that urea switches on genes involved in building a healthy skin barrier, including the one for filaggrin, a protein that’s crucial to the structure of the skin’s outer layer and its barrier. That’s an interesting finding, but it’s lab evidence about mechanism, not proof that a given cream repairs your barrier.

What Canada allows

Health Canada’s Cosmetic Ingredient Hotlist restricts urea in cosmetics. Apart from bath products that are diluted in water, cosmetics can contain up to 10 percent urea. Stronger urea products exist, but they fall outside those cosmetic rules. If you need one for very thick skin, ask your pharmacist.

For most people with ordinary dry skin, the 10 percent limit is not a drawback. The review notes that 10 percent is the strength used most often in studies of dry skin.

What the evidence shows

Dry skin

The 2021 review summarizes many clinical studies of urea for xerosis, the medical term for dry skin. A few examples:

• In older adults, whose skin often gets drier with age, a 5 percent urea cream increased skin hydration compared with a control moisturizer in a study of 42 people over 60.
• In small studies, 15 to 20 percent urea creams reduced transepidermal water loss, the amount of water that evaporates through the skin.
• For dry feet in people with diabetes, a 10 percent urea moisturizer improved dryness faster than a comparison cream.

Many of these studies are small. It’s also worth knowing that the review was written partly by authors employed by, or paid consultant fees by, a company that sells urea creams.

Eczema

The evidence is more modest here. A 2017 Cochrane review, which pooled randomized trials of moisturizers for eczema, found that in one study people using a urea cream reported improvement more often than those using a placebo cream, and dryness improved more often in the urea group. One small study found fewer flares. But more people using urea reported side effects, and the overall quality of evidence ranged from low to moderate.

The 2021 review adds that a trial of 172 people found that a 5 percent urea preparation lengthened the time without eczema and cut the risk of relapse. Promising, but not a reason to expect urea to outperform other good moisturizers.

Why urea can sting

Stinging is urea’s best-known downside. DermNet notes that urea and other acidic preparations often sting if applied to scratched or cracked skin. The Cochrane review lists smarting and stinging among the side effects reported with moisturizers.

The 2021 review describes urea as well tolerated overall, with mild, temporary irritation that’s more common at higher strengths. It also notes that some urea creams have a faint smell that fades quickly.

To keep stinging down:

• Start with a low strength, especially on the face or on sensitive skin.
• Don’t apply it to open cuts, deep cracks or freshly scratched eczema. Use a plain, bland moisturizer there until the skin heals.
• Keep it away from your eyes.

If a urea product stings for more than a few minutes or leaves your skin red, stop using it. If your dry skin or eczema isn’t better after two weeks of regular moisturizing, see your doctor or pharmacist.

Getting the most from a urea moisturizer

• Apply right after a bath or shower, when your skin still holds water. DermNet notes that moisturizers are most effective then.
• Use it regularly. Dry skin improves with steady use, not a single application.
• Match the strength to the job: a lower strength for general dryness, a higher one for rough heels, elbows and knees.
• In a Canadian winter, when indoor heating dries the air, you may need it more often.

You can browse the panel’s reviewed moisturizers or filter for products that support the skin barrier.

The bottom line: urea is a modest, well-studied ingredient that your skin already relies on. At low strengths it helps skin hold water; at higher strengths it also smooths rough, thick patches. It has good support for dry skin and some support for eczema, it can sting on broken skin, and in Canadian cosmetics it tops out at 10 percent.