A black line on your nail (medically known as melanonychia) causes a streak of dark pigmentation that runs along the nail bed. It can be a normal color variation, especially in people with darker ...

She explains that the appearance of the brown band on a nail "is something for which you should always consult a dermatologist" about. It is called longitudinal melanonychia and can have multiple ...

Onychomycosis, or fungal infection of the nail, most often affects the toenails. Infected nails usually have a thick, yellow appearance and can become coarse and brittle (see Figure 4).