Alopecia and hair loss mean the same thing; reduction in hair density and increased hair fall. This can be a diffuse process or occur in localised areas on the scalp or other areas of the body. It can occur slowly over many years, or be rapidly progressive, occurring over days or weeks. There are many causes for alopecia which can broadly be grouped into three categories: internal deficiencies, scalp disease or ‘other’ causes. The most important distinction is whether scarring is a feature or not, because this will dictate how successful treatment can be.