Fungal infection in the nails is caused by an overgrowth of fungi in your nails. When the growth of fungus happens on the fingernails or toenails, it is known as onychomycosis or tinea unguium.
Here are the probable causes of why you might get a fungal nail infection:
1. Diabetes
2. Problems in your circulatory system
3. Age
4. Artificial nails
5. Swimming in public pools
6. Nail injuries
7. Skin injuries surrounding the nail
8. Fingers or toes, which have been moist for an extended period of time
9. Immune system problems
10. Wearing shoes which have enclosed toes
It is also worth noting that fungal infections happen much more frequently in your toenail as compared to your fingernails, this is because of two main reasons. Firstly, that the fungi can grow very easily on your toenails because of the position as your shoes are dark, warm and moist and therefore, perfect for the growth of fungi.
The second reason for more fungal infections on your toenails as compared to your fingernails is because toes have less blood flow than fingers, thus making it harder for the immune system to fight off the infection.
Fungal infections in your nails are one of the easier infections to diagnose. This is because there are several symptoms which indicate you have this condition.
Here are some of those symptoms:
1. Scaling underneath your skin
2. White or yellow streaks on your nails
3. Corners of the nail may crumble
4. Flaky surface of the nail
5. Yellow spots at the bottom of the nails
6. Loss of nail
7. A nail breaking off from the rest of the nail
8. An odor from the nail
9. Brittle or thick nails
Ref : Lybrate