Clinical Dermatologists are unlikely to see more than 20 different hair diseases during their careers. The most common diseases that Dermatologists are likely to see are androgenetic alopecia, alopecia areata, telogen effluvium, trichotillomania alopecia, hair shaft defects from cosmetic processing and excess hair growth (hirsutism or hypertrichosis). Most hair diseases are very rare and occur in less than 1% of the population.

One of the main criticisms from patients is that their dermatologist just does not understand their particular disease but because of the limited research into hair disease it is very difficult to make a specific diagnosis. Because of limited research there are very few diagnostic tests or treatments available other than for the most common diseases.

To define a disease and appropriate treatment a dermatologist uses a process of deduction from clues that he gets from the patient. There are three main methods of information gathering. A dermatologist will ask questions regarding the history of your hair loss and questions in regards to your life style. He will conduct a visual examination of your hair and occasionally take sample of hair, skin and blood for further testing and examination.

The first most common question will be 'How long have you had hair loss?'. This will determine if you were born with it or acquired it in later in life.

The visual examination of the hair only takes a couple of minutes, as hair loss is clearly visible. The first thing a dermatologist will check is the pattern of the hair loss and then the form of the hair loss.

If a fungal infection is suspected the dermatologist may look at the hair under a light source called a Wood's Lamp.

A hair pull test may also be conducted. The dermatologist gently pulls on a few strands of hair to see if the fibers pull out easily.

A few fibers of hair may be taken for a microscopic analysis. The hairs have to be pulled out rather than cut so that the roots of the fiber as well as the shaft can be examined.

If it is suspected that the hair condition is the result of bacteria, yeast or fungi the dermatologist will take scrapings of skin from the affected area. Some of these scrapings will be covered with special staining chemicals that bind to certain types of bacteria or fungi.

Occasionally a dermatologist will take a scalp biopsy. This he will send to a histologist who cuts the biopsy into thin sections and lays them on a microscopic slide. The skin sections can be stained in different ways depending on what is being looked for.

Internal body dysfunction may also cause hair loss or excess hair growth. If a dermatologist suspects that hormones or the immune system are involved he may take a blood sample and may even ask you to see an endocrinologist/immunologist for further testing.