Dark colored streaks on toenails are common in the United States, especially among people with darker skinned toes, particularly African Americans. For the most part, these stripes generally represent non-serious conditions. However, especially in fair-skinned people, the presence of these stripes could represent a deadly cancer. This article will discuss the common causes or dark streaks on toenails and which condition is cause for alarm.
Before we begin, the reader should keep in mind when reading this article that the information contained is not intended to provide specific medical advice for the medical condition itself, but is intended to be a general discussion on this health topic. Any specific questions or concerns about the conditions described in this article should be directed to your GP or specialist for proper diagnosis and treatment.
The toenail is a dense tissue made of compressed keratin. The nail plate itself begins at the nail matrix, which is essentially the root of the nail. The outer edge of the matrix looks externally like the lunula, or the white semicircular area at the base of the nail just beyond the cuticle. The nail grows slowly outward, sliding semi-loosely along the skin. The color of the nail itself is a kind of dull white or cream, with some clarity to see the skin under it. Solid white, yellow, blue, brown, or black discolorations on the nail plate are abnormal and represent a pathological process. The most common sources of toenail discoloration are keratin debris accumulated under the nail due to natural thickening and aging of the nails, as well as discoloration from a fungal infection. These typically create a white, yellow, or yellow-brown discoloration. Since both extensive topics have been covered by this author in other articles, the causes of the darker shades of discoloration will be presented here.
Dark toenail discoloration has several causes, and properly diagnosing the cause is key to successful treatment. The most common reason that nails turn dark in color is due to bruising under the nail. Bruises are essentially blood that leaves bleeding. It can occur under the skin and can also occur under and on top of the skin located directly under the toenail. Bleeding under the toenail can be caused by a heavy object falling on the toe, pressure from tight shoes, toes stuck in the toe of the shoe as often seen in runners, and by blows that cause blood vessels to burst. Spontaneous rarely occurs, and often if one does not recall injuring their toe, it usually means that the injury was mild enough not to cause memorable initial pain. The bruise under the nail remains on the nail plate until it grows with the nail.
Bruises that do not grow as the nail continues to grow are cause for concern and a podiatrist should be contacted. The possible cause of this will be discussed later. When the bruise occupies less than a quarter to a third of the nail, it is likely to be left alone and the nail allowed to grow out. If the bruise is more extensive and covers the entire nail area, the nail plate should be removed. This is done for two reasons. First of all, it allows the blood to drain properly and limits the amount of damage that bleeding caused to the nail root when slightly lifting the nail plate during the active bleeding time. Second, the bleeding may have been caused by a deep cut in the skin under the nail plate during the initial injury, and this skin should be evaluated for any cuts that need to be sutured. Another concern, especially if a fracture has occurred in the bone under the nail, is the pieces of bone that protrude from the skin externally. If they are not removed and the skin is cleaned and treated properly, an infection can develop that can spread to the underlying bone.
Another cause of dark discoloration is infection. As mentioned above, fungi can enter the skin under the nail and cause discoloration, thickening, brittleness, and debris. This fungus is the same in the same group of organizations that causes athlete’s foot, and from a color perspective it can change the nail from dull to solid white, yellow, gray, brown, or even black in some cases. Treatment is somewhat complex, as only certain medications have scientifically proven efficacy, and many home treatments are still used that simply show no real value. Another source of infection is bacteria, specifically bacteria from a family of organisms called Pseudomonas. This bacteria is prone to invade skin that has been damp for a while and is commonly spread in hot tubs and hot tubs. The bacteria create a green color change on the skin and nail tissue, presumably from the iron pigment. The so-called green nail syndrome is common and is treated with a special solution of diluted vinegar (acetic acid) or with specific antibiotics directed against pseudomonas. This infection rarely progresses to a more serious condition in otherwise healthy people and is usually easily treated.
Nail discoloration moving across the nail in a thin line from one side to the other has many different causes and many to discuss in detail. Causes can include kidney disorders, certain mineral deficiencies, toxic metal poisoning, heart disease, cancer chemotherapy, certain chronic medications, and major injuries to the body. Due to the wide variety of causes, a visit to your primary care physician, dermatologist, or podiatrist is recommended. Usually there is no immediate treatment for these lines, but the doctor can diagnose another condition that needs treatment by examining the nail, especially if something like metal poisoning or mineral deficiency is not diagnosed.
Nail discoloration that travels in a streak from the beginning to the end of the nail is the symptom of most concern. This streak is typically brown, dark blue, or black, and can be found on one side of the nail or in the center. Usually this streak takes up less than a quarter of the width of the nail, although in some cases it can be wider. The usual cause of this streak is the overproduction of cells that produce skin pigmentation, also called melanocytes. These cells produce melanin, which gives darker skinned people their skin tone and Caucasians their tanned skin. It naturally protects the skin from the sun’s harmful ultraviolet rays, although overexposure to the sun can cause a mutation in the production of melanocytes. This is technically a cancerous growth. In most cases of nail spots and skin conditions such as moles, this is a benign growth. However, a malignant cancer can develop that has the potential to spread to other organs and lead to death. This cancer is called melanoma and it is deadly. Dark streaks that start at the cuticle and travel the length of the nail are very common in people with darker skin tones, particularly African-Americans.
In fact, many people have stripes on almost all of their toenails and have had them since they were born. They usually do not represent melanoma of the nail and are usually benign. When these streaks develop recently in Caucasians, or if there is a new growth or change in a pre-existing streak in someone with darker skin, the nail and the skin surrounding the nail should be evaluated by a doctor. This is especially true if skin discoloration is developing next to the nail, no matter what the original skin tone is. A biopsy of the scratched part of the nail, the root of the nail, and the surrounding area of the skin is necessary to make sure there is no malignant cancer. This is a simple procedure, usually performed in an office by a podiatrist, dermatologist, or sometimes a general surgeon or family doctor, and it heals quickly. Usually the nail grows back healthy if the condition was benign. If melanoma is present, immediate attention should be paid to the toe to prevent further spread. This usually includes amputation of the tip of the toe or the entire finger, depending on the size of the melanoma. This is absolutely necessary to save life and prevent the spread of cancer.
As you can see, dark toenail discoloration can have a number of different causes. Most are benign and resolve with simple treatment. Some are simply genetic, like the common streaks on the nails of darker-skinned people. Others are dangerous cancers that need immediate treatment. Due to the potential for cancer, this author recommends that a doctor evaluate all areas of dark discoloration on the nails to make sure the condition is benign. The least you lose is a little time in the doctor’s office, and in the best of cases, it can save your life.