Glycerin vs Urea (Cosmetic): which is worse?

What is Glycerin?

Glycerin is a simple polyol (sugar alcohol) that is colorless, odorless, and viscous. It naturally occurs in all animal and vegetable fats and is the backbone of triglyceride molecules. Cosmetic glycerin is typically derived from vegetable oils (plant-based) or as a biodiesel byproduct.

What is Urea (Cosmetic)?

Urea is a naturally occurring organic compound that is a byproduct of protein metabolism, found in urine and skin. In cosmetics, synthetic urea is used at varying concentrations for different effects: 2–10% as a humectant; 10–20% as a keratolytic (softening/exfoliating thickened skin); 20–40% for calluses and nail penetration.

Documented risks

Glycerin: Glycerin is one of the safest cosmetic ingredients known, with centuries of use. The CIR has repeatedly confirmed its safety. It is non-irritating, non-allergenic, and non-toxic. At very high concentrations in leave-on products (>30%), it can have a dehydrating paradox effect — pulling water from the dermis if the environment is very dry — but this is not a health risk. It is safe for all ages including infants.

Urea (Cosmetic): Cosmetic urea is safe and has been used for decades in dermatology for very dry and keratotic skin conditions. The CIR has confirmed safety at cosmetic concentrations. At concentrations above 10%, it may cause mild stinging on broken or inflamed skin. No carcinogenicity or hormone disruption is documented. Urea is considered an active ingredient in OTC skin softeners in Europe.