In normal, healthy people, fungal nails are most commonly caused by a fungus that is caught in a moist, wet area. Gyms and swimming pools are common sources. Athletes have been proven to be more susceptible to fungus due to the wearing of tight-fitting, sweaty shoes and repetitive trauma to the toenails.
Elderly people and people with certain underlying disease states are also at higher risk. Anything that impairs your immune system can make you prone to getting infected with the fungus. These include conditions such as AIDS, diabetes, cancer, or taking any immunosuppressive medications like steroids.
What Are the Signs and Symptoms of Fungal Nails?
There are many species of fungi that can affect nails. By far the most common, however, is called Trichophyton rubrum. This type of fungus has a tendency to infect the skin (known as a dermatophyte) and manifests in the following specific ways:
- Starts at the ends of the nails and raises the nail up. This is called "distal subungual onychomycosis." It is the most common type of fungal infection of the nails (90%). It is more common in the toes than the fingers. Risk factors include older age, swimming, athlete's foot, psoriasis, diabetes, family members with the infection, or a suppressed immune system. It usually starts as a discolored area at the corner of the big toe and slowly spreads toward the cuticle.
- Starts at the base of the nail and raises the nail up. This is called "proximal subungual onychomycosis." This is the least common type of fungal nail (3%). It is similar to the distal type, but it starts at the cuticle (base of the nail) and slowly spreads toward the nail tip. This type almost always occurs in people with a damaged immune system.
A less common fungus that can affect toenails is yeast onychomycosis. This type of infection is caused by a yeast called Candida and not by the Trichophyton fungus named above. It is more common in fingernails and may be the most common cause of fungal fingernails. Candida can cause yellow, brown, white, or thickened nails. Some people who have this infection also have yeast in their mouth or have chronic paronychia that is also infected with yeast.
Conditions That Can Be Mistaken for Nail Fungus
The following toenail conditions are often mistaken for fungal infections:
- Lines and ridges. They may worsen during pregnancy. In fingernails, a large groove down the center of the nail can be caused by nail biting.
- Senile nails. As you age, the nails become brittle and develop ridges and separation of the nail layers at the end of the nail. Try to avoid cleaning solutions, and don't soak the nails in water.
- Whitish or yellowish nails due to onycholysis. This means the separation of the nail from the nail bed. The color you see is air beneath the nail.
- Red or black nails. These are usually due to a hematoma, or blood under the nail, and occur from trauma. The discolored area will grow out with the nail and be trimmed off as you trim your nails. If you have a black spot under your nail that was not caused by trauma, you may want to see a dermatologist to make sure it is not melanoma.
- Green nails. This unusual color can be caused by Pseudomonas bacteria, which grow under a nail that has partially separated from the nail bed.
- Pitted nails. Psoriasis or other skin problems that affect the nail matrix, the area under the skin just behind the nail, can cause pitted nails.
- Swelling and redness of the skin. When the skin around the nail is irritated, it is called paronychia. This is an infection of the skin at the bottom of the nail (cuticle). If the infection is acute (has a rapid onset), it is usually caused by bacteria
- Chronic nail trauma. Athletes who are repeatedly starting and stopping, kicking, and other athletic endeavors, can cause damage to the nails that can look a lot like fungal nails.
Your podiatrist can determine if you have a fungal infection in your toenail or one of these other conditions.