Sooner or later, every person caring for a baby comes bum-to-face with nappy rash, that collection of redness and sometimes blistery nodules that appears out of nowhere from underneath a dirty nappy.
Usually there's no one cause, but a variety of factors that combine to make the right conditions: a warm and humid environment, friction and prolonged skin contact with urine and faeces.
These conditions are, of course, present in every nappy. In practice, that means that at any given moment, around 1 in 4 of all babies and toddlers have a nappy rash, according to Britain's National Health Service.
So what, if anything, can parents do to avoid nappy rash? Or should they just accept it as inevitable?
"Nappy-free times during the day are a first step," says paediatric dermatologist Prof. Regina Fölster-Horst, who says nappy rash can be avoided in the right conditions.
Even if it brings the risk of an accident, giving a child some time to air out every day will reduce the risk of nappy rash. You may want to avoid this time on carpets, beds or other surfaces that are difficult to clean.
"Nappy changing should also be done at intervals of two to three hours," Fölster-Horst says.
How you clean your child can also make a difference. Wet wipes containing fragrances, preservatives and alcohol will only further irritate the sensitive skin.
Instead, you're better off using water and mild soaps for cleaning the nappy area, and disposable wipes with oil are suitable for removing faeces.
Special creams and ointments, such as those based on zinc, can provide relief. But these measures are not always successful.
When is time to visit a doctor? "If there is no improvement after a few days of this therapy, the skin is always irritated, skin changes can be seen in another skin area or pustules appear in the wound area," Fölster-Horst says. – dpa