The term applies to red skin which occurs due to the nappy being too tight or saturated with urine. Add some boric acid, (say 500 mg to half tumbler of water) to water and wash the skin and then dry up with a soft towel or cloth. You may apply some baby cream or Vaseline. In summer, the child often sweats a lot--- in that condition also do as is advised above. Never tie a wet nappy to the child, as it may cause itching, irritation and other skin diseases.