Nappy rash is a common inflammation of the napkin area (bottom, genitals, groin). In an infant. It can range from mild irritation to a gross infection. In simple terms it can be thought of a simple progression. In its simplest form the irritation is chemical. Urea in urine in the nappy is converted by bacteria from faeces (poos) into ammonia which burns the skin. Thus it is like a chemical burn to the groin. If the irritation persist there may be an overgrowth of a fungus called candida which leads to thrush. Thrush is also caused by antibiotics taken by the baby or breastfeeding mother. Lastly the irritated skin can also become infected by skin bacteria leading to a bacterial skin infection.
The treatment of nappy rash also depends upon the extent of the rash. The simple irritation is first treated with barrier creams which are designed to prevent urine and faeces from being in contact with skin. The most widely used of these is zinc and castor oil. Obviously this has been around for a very long time but it still works well in mild rashes. If the rash is more severe you may need to use a mild steroid cream containing hydrocortisone. This will settle down the swelling but will need to be used in conjunction with a barrier or in a barrier or ointment base.
If thrush complicates the issue then an antifungal or antithrush cream/ointment is needed. This will often be in combination with a steroid. If the rash is very severe and also complicated by bacterial infection then an oral antibiotic will probably be prescribed by the doctor. But obviously you can start to chase your tail with stomach upset due antibiotic for the rash.
In general terms all babies will sufer from nappy rash sometime in their infancy and some are worse than others. To prevent the rash from occurring you need to change baby regularly and if make sure the nappy region is completely clean and dry with each change. Try to avoid soaps and detergents and use a barrier cream if a rash begins to appear. Generally rashes can be controlled if treated early. However like forest fires they do get out of hand really fast and so if you are at all concerned see your doctor sooner rather than later.