Why are my toe nails turning black?

I used to have normal coloured finger and toe nails. They were long and strong and almost everyone who knows me used to admire them. I don’t like painting my finger nails but my toe nails are always manicured. However, about four months ago, I noticed my nails were changing colour to something very disturbing - especially the big one. It now has this gray colour. Also, when I wear closed shoes, by evening I feel like it (the big nail) was hit by something. The pain is so bad I have now stopped wearing closed shoes. I am worried that it might fall out sometime. I no longer go for pedicures as I am too embarrassed to let the manicurist see my nail…so I paint them myself because they are hideous to look at without nail polish. What is going on? Alicia Dear Alicia The most common cause for discoloration of nails is fungal infections. These occur due to fungal spores present in the atmosphere. This is a very slow growing infection and is noticed only when evident discoloration occurs. Dampness of the hands and or feet is the common reason for inducing this infection. Wearing nylon socks, damp socks, closed shoes for a long time, walking bare foot on damp surfaces like around swimming pools, not drying the hands properly after washing, are common factors which precipitate and aggravate this infection. It may be secondary to fungal infection elsewhere in the body. Immune depressed conditions like diabetes, HIV/AIDS, renal diseases, increase susceptibility to fungal infections. Bacterial infections like pseudomonas can cause painful and discoloured nails. Smokers tend to have discoloured nails due to chronic deposition of carbon present in cigarette smoke over nails. Frequent use of nail paint which is not removed completely before each application can discolour the nails. Discoloration of nails can also occur due to systemic chronic diseases like liver and kidney diseases. But in these cases, along with discoloured nails, there would be other symptoms like loss of appetite, nausea, vomiting, and swelling over face and feet e.t.c. Malnutrition, particularly deficiency of proteins and iron, vitamins B12 and or D in the body, any one or more of these can cause weak and discoloured nails. You need to keep the hands and feet clean and dry to prevent fungal infections. A balanced nutritious diet is also beneficial. Avoid nylon socks and wear cotton socks instead as nylon tends to aggravate foot infections. Use of closed shoes for long hours together, which prevents ventilation of the feet, should be avoided. Use of nail paint should also be avoided for some days as it will tend to mask infection. Get a blood sugar test done to exclude diabetes. If present, then high blood glucose levels need to be controlled to control the infection. Use of antifungal drugs like ketoconazole or flucanazole for about 10 to 14 days helps to clear the infection initially. Antifungal ointments do not penetrate the nails easily because they are brittle, hence not very effective. They can be used after the infection starts clearing. Treatment of fungal infection of nails has to be taken for at least nine months for total eradication of the fungus. Simultaneous use of anti inflammatory drugs like brufen or diclofenac for a short period, say five days, will help reduce the pain. In case of bacterial infection of the nails, antibiotic and anti inflammatory drugs have to be taken to clear the infection. Dr. Rachna is a specialist in internal medicine at Ruhengeri Hopsital