Baby skin has the same number of layers as adult skin but each layer is considerably thinner. Overall baby skin is just one-fifth of the thickness of adult skin.
The outermost layer of the epidermis (the horny layer) is much thinner and the cells are less tightly packed than in adult skin. The sweat and sebaceous glands are also less active than in adults, so the hydrolipid film (an emulsion of water and fats that covers and protects the surface of skin) and the protective acid mantle (the water part of the hydrolipid film, which is mildly acidic) are still relatively weak.
As a result, the barrier function is limited:
- Baby skin is less resistant than adult skin and especially sensitive to chemical, physical and microbial influences: Substances that come in to contact with baby skin are absorbed more easily and penetrate into deeper skin layers.
- Baby skin is prone to drying out.
- Baby skin is more sensitive to UV rays than adult skin.
Sensitivity to UV is further enhanced by low pigmentation in baby skin. Melanocytes (the cells responsible for melanin production) are present, but less active.