Dark-colored streaks in toenails are common in the United States, especially amongst people with darker skin toes, particularly in African-Americans. For the most part, these streaks usually represent non-serious conditions. However, especially in fair-skinned people, the presence of these streaks could represent a deadly cancer. This article will discuss the common causes or dark streaks in toenails, and what condition is cause for alarm.
Before beginning, the reader should be aware while reading this article that the information contained is not meant to provide tailored medical advice specific for one's own medical condition, but is meant as a general discussion on this health topic. Any specific questions or concerns for the conditions described in this article should be directed to one's own general physician or specialist for proper diagnosis and treatment.
The toenail is a dense tissue made of compressed keratin. The nail plate itself begins in the nail matrix, which is essentially the root of the nail.
The outer edge of the matrix is seen externally as the lunula, or the white semi-circular shaped area at the base of the nail just beyond the cuticle. The nail slowly grows outward, sliding semi-loosely along the skin. The color of the nail itself is a kind of opaque white or cream, with some clearness in it to see the skin below it. Discolorations in the nail plate, be they solid white, yellow, blue, brown, or black, are abnormal and represent a disease process.
The most common sources of toe nail discoloration are due to keratin debris built up under the nail from natural nail thickening and aging, as well as discoloration from a fungus infection. These typically create a white, yellow, or yellow-brown discoloration. Since both of these lengthy topics have been covered by this author in other articles, the causes of darker shades of discoloration will be presented here.
Dark toenail discoloration has several causes, and properly diagnosing the cause is key to a successful treatment. The most common reason nails become darkly colored is because of bruising under the nail. Bruising is essentially blood left behind by bleeding. It can occur under the skin, and can also occur under and over the top of the skin located directly under the toenail.
Bleeding under a toenail can be caused by dropping a heavy object onto the toe, by pressure from tight fitting shoes, by toes jamming into the end of the shoe as seen often in runners, and by stubbing injuries that cause blood vessels to burst. Spontaneous rarely if ever occurs, and often if one does not remember injuring the toe it usually means the injury was minor enough not to cause initial, memorable pain. The bruising under the nail stays in the nail plate until it grows out with the nail.
Bruises that do not grow out as the nail continues to grow are cause for concern, and a podiatrist should be contacted. The potential cause for this will be discussed later. When the bruising takes up less than a quarter or a third of the nail, it can likely be left alone and the nail can be allowed to grow out. If the bruising is more extensive, covering the entire area of the nail, the nail plate should be removed.
