Updated December 15, 2014.

How do I know if I have a toenail fungus?

Toenail fungus, also known as onychomycosis, is a slow-growing infection that most often spreads underneath the nail. The most common signs of a toenail fungal infection are a thickening of the toenail, a brown or yellow discoloration of the nail and flaky debris under the nail. Sometimes there are white patches on the surface of the nail, but this is a less common form of nail fungus

I took anti-fungal pills as prescribed and they didn't help at all. My toenails are still thick and ugly. What would cause this?

The oral anti-fungal medications reach the fungus where it thrives - the area under the nail. However, even though the medication may have eradicated the fungus, it won't improve the look of the infected parts of the nail right away. As the new, healed nail grows out and the thick, discolored nail is trimmed away, you should see a gradual improvement in the nail's appearance over the next few months.

Possible reasons for a lack of toenail improvement after a prescribed course of oral anti-fungal medication include:

• The thickness or discoloration of your nail was caused by something other than a fungal infection. Other common causes of nail thickness and discoloration include trauma and such medical conditions as diabetes and hypothyroidism.
• The fungus causing the infection was resistant to the medication.

I just started an intense CrossFit routine in new running shoes. Now, part of my big toenail is turning black and I think it's coming loose. What should I do?

The most likely cause of a sudden black discoloration and loosening of a toenail is trauma to the nail's matrix, or growth area.

This would cause bleeding beneath the nail, which appears as a black discoloration. It may be that your new shoes are too tight or loose, which can lead to more friction against your toe as you work out. Sudden-onset dark discoloration and loosening of a toenail may also be caused by a bacterial or fungal infection. In any case, it is best to have any toenail color changes or toenail loosening evaluated by a podiatrist or other physician. Black or brown discoloration of a toenail should always be evaluated. In some cases, although infrequent, these changes may be signs of the skin cancer melanoma.

A few years ago I dropped a weight on my toe, and the nail has been thick ever since. If I have it removed will it grow back normal?

Having a thick or otherwise damaged toenail removed surgically will probably not result in a healthier nail growing in its place. Once a nail's growth center (nail matrix) is damaged, it usually continues to produce a thickened or disfigured nail.

I had a pedicure for the first time a few days ago. Now the skin next to my toenail is red and itchy. Could this be an infection?

Those are likely signs of an infection, especially if the nail's protective cuticle was cut or pushed back during the pedicure. Another possible cause of redness and itching of the skin is an allergic reaction to a product that may have been used in your pedicure (for example, nail polish or cuticle remover creams). It is best to seek medical treatment as soon as possible.

My daughter keeps getting ingrown toenails. Is it because she is not cutting her toenails straight across?

The most common reason some people are prone to recurrent ingrown toenails is due to the shape of the big toe and underlying bone position. Other factors that can make someone get frequent ingrown toenails are shoes or socks that are too tight around the toes or shoes that are too loose, which allow a foot to shift around and rub the side of the shoe. As long as your daughter isn't cutting her toenails so short that they bleed or hurt, it's okay to cut a slight curve in the nail. Sometimes bone spurs can lead to recurrent ingrown toenails. These would be seen on an X-ray of the toe.