What Causes Black Spot Under Toenail?

Have you just noticed a black spot on toenail? You need not be alarmed. It is simply a sign that you might have a foot injury, a nail infection or an underlying condition. This is normally a cosmetic issue instead of a medical one. The black spot can be unsightly and can cause embarrassment when you do not have your shoes on. So what causes these unsightly dark spot under toenail? How do you get rid of them? Find out below.

Causes and Treatments for Black Spots on Toe Nail

1. Toenail Injury

This should be the first consideration after you have a black spot. Establish what might have caused the injury. Possible causes range from stubbing a toe to dropping a heavy object on your nail. The black spot is caused by broken capillaries under the nail.


Take painkillers and apply a cold compress to the injured toe. If the injury is severe, you might lose your nail. However, the spot should clear as your nail grows.

2. Runner's Toe

Runner’s toe is caused by wearing shoes that do not fit. The pressure built up by each step while running causes injury to the toenail.


The first step would be to get new shoes. If the pain is not severe, you can ignore the black spot on toenail as it will heal by itself. Remember to take a day or two off from running. Make sure to keep the area clean and dry. You can get back to running once the pain is bearable.

To prevent recurrence, wear shoes that are one-half size bigger than your foot. Make sure your toe nails are kept trimmed just enough to avoid exposing the injured area. You should lace your shoes tight if you’re running downhill.

3. Bacterial Infection

Black or green spots on your toenails could be a bacterial infection. It is normally caused by bacteria called Pseudomonas aeruginosa. The bacteria can affect any part of the body. The bacterium is never a problem until it gets in between nail bed and nail plate after your skin breaks.


The most outstanding symptom of bacterial infection causing black spot on toenail is the sweetish smell the infected area produces. You should see a dermatologist for treatment.

To help with the healing process and to avoid future infection, do not wear open toe shoes all the time. Do not walk in the dirt and grass barefoot. Eliminate any bacteria in the nail folds by cleaning out debris with a soft toothbrush.

4. Fungus Infection

Also referred to as onychomycosis, nail fungus can cause black spot. This is accompanied by a yellow discoloration and brittle, crumbling or distorted nails.


5. Skin Cancer

Black spot on toenail can also be caused by acral lentiginous melanoma. This is a type of skin cancer that often appears on the big toe. The affected area may have vertical borders that change with time.

For more info on causes and treatment of black toenail, check out the video below: 

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