Black toenail cover may be related to subnail hemorrhage, onychomatous mole and onychomelanoma and other diseases.
1. When the blood vessels under the nail rupture and bleed as a result of trauma, the blood is not discharged in time and will be pooled under the nail, which makes the toenail appear black. With the absorption of the blood, the black spot phenomenon can be improved gradually.
2. Nail nevus is a kind of benign tumor located in the region of nail matrix of toenail, which is mainly manifested in the clinic as black vertical stripes on the nail plate, with uniform pigmentation and clear boundary.
3. Nail melanoma is a kind of malignant tumor, which may be worsened by onychomatous nevus, and may be manifested as black spots on the toenail, and there may be bleeding, erosion, or even ulceration, and so on.
For the black spots appearing under the toenail for a long time, it is necessary to have regular review and timely treatment if necessary.