Dear Doctor,

My toe nails have continuously grown darker and darker. What could be the cause?

Emma

Dear Emma,

The most common cause for dark discoloration is fungal infection of the toes. This can occur due to chronic dampness of the feet. Most common reasons for this is use of damp shoes, damp socks, nylon socks, walking without shoes on damp lawns or pool sides. Plastic shoes and sandals also increase susceptibility to fungal infections.

Persons with reduced immunity like those with diabetes or HIV are more prone to develop this kind of infections and in a more severe form. Once the nails are infested by fungus it tends to accumulate and grow over time, thus the dark coloration increases slowly. The diagnosis can be confirmed by examining a scraping from the nail under the microscope. It is curable by use of suitable anti fungal drugs preferably tablets(ointments cannot penetrate nails).

Trauma can also cause black discoloration of nails, due to accumulation of blood below nails. Here the toes would be painful and gradually the nail may fall off. Chronic mild trauma caused due to ill fitting tight shoes can also result in progressively black coloration of nails. Rarely bacterial infections can cause toe discoloration. But in such cases the toe will be swollen and extremely painful due to collection of pus below nails. Slowly the nail will fall off, otherwise removal of nail will release the pus helping in cure.

It is better to keep feet clean and dry, avoid use of tight fitting or damp and or plastic shoes, prefer cotton over nylon socks. These measures will prevent fungal infections and black coloration of toes.

Dr Rachna Pande  is a specialist in internal medicine at Ruhengeri Hospital