Athletes will often encounter a problem with their toenails turning dark. It is due to the toes hitting the end or the top of the shoe toe area. Quite often the toenail may become loose and fall off. This can also occur in people who have worn a tight shoe for a prolonged period of time. The dark color is a result of bruising under the toenail. Generally it is not painful. The damaged cause to the toenail may allow the establishment of a fungal infection in the nail. In people who have diabetes, any change in the color of the toenail should be evaluated by a doctor. The pressure, which caused the bruising of the nail, can cause a small sore under the toenail, which can become infected.
Treatment might consist of trimming the loose nail back and applying a topical anti-fungal medication. If the skin under the nail is ulcerated, then a topical antibiotic ointment should be applied. Patients with diabetes should not treat this condition themselves and should seek the advice of a doctor.
Prevention consists of wearing properly fitting shoes and possibly stretching of the calf muscles. People who are involved in athletics and exercise often have excessively tight calf muscles. This results in the muscles in the front of the leg having to work harder to pull the foot upward. This forces the toes to impact the top of the toe with greater force, potentially causing the bruising of the toenail.