The sweat, urine and the stool increases the pH of the skin and the putrefying enzymes that are produced makes the outer layer of the skin permeable to the germs which in turn causes skin irritation. The ammonia in the urine also damages the skin.
When plastic non-porous diapers are used the moisture can irritate the skin causing the diaper rash.
The diaper rash could also occur if the skin of the baby is sensitive to the detergents used to wash the diapers.
