What causes fingernails to turn black?

There are many reasons why fingernails turn black. In addition to trauma, this condition may be caused by a lack of trace elements. You can go to the hospital to check trace elements. Of course, the best way to supplement is to take vitamin B complex at the same time as treatment. Fingernail blackening may also be caused by onychomycosis, onychomycosis mainly causes nail blackening, but also causes fingernail thickening, may be caused by congestion under the nail onychomycosis, which is a disease caused by fungal infection symptoms, the disease has a strong infectivity is likely to be transmitted to their relatives and friends, so get onychomycosis must be treated as soon as possible. Suggest to eat more fruits and vegetables, do not eat spicy food. But suggest you had better go to the hospital to check, clear cause is better.