Dandruff is a disease in the skin that primarily affects the scalp. Symptoms include flaccidity and sometimes mild itchiness. Seborrhoeic dermatitis is called a more severe form of the condition, including inflammation of the skin. While the cause is unclear, a number of genetic and environmental factors have been identified, the condition may deteriorate in the winter. The underlying mechanism involves the excessive growth of cells in the skin. It is not because of poor sanitation. The diagnosis is symptomatically based.