#1 A brown vertical stripe on the nail
The majority of the time, benign moles or pigmentation will be the main cause of a dark brown or black line along your nail or brown pigments around the nail.
People with darker skin experience this more often due to their increased melanocytes. A brown, lengthwise band can be seen in the nail when the melanocytes, which are normally triggered by stress to the cuticle, start producing pigment.
However, you should be careful since this stripe could be a melanoma warning sign. Even though you might assume the most deadly kind of skin cancer always manifests as a mole or other dark spot, it can really begin in the nail.
While just 1% of melanomas in Caucasians start in the nail, for African-Americans, 20% of melanomas develop right there. In more severe situations, it may spread to the tissue around the nail or the area around the cuticle. That is a concerning sign since it indicates that it is spreading and growing.
