Infected Toenail – Types, Pictures, Causes of Toenail Infection

Toenails are made up of a protein known as keratin, which is also the main component of hair and the outer layers of skin. Keratin is highly compacted in the nails to form a tough protective layer at the tips of the fingers and toes. Not only is it able to withstand force, it is also able to resist various microbes. Despite being hardy, it can still be damaged, detached and infected.

What is an infected toenail?

An infected toenail refers to two types of infections – an infection of the nail itself or of the surrounding skin. This is mainly due to fungi or bacteria. The toenail may be thick and hardy but it is prone to infections for several reasons. With nail infections itself, the nail is gradually damaged over months and years and eventually destroyed. With infections of the surrounding skin, the infection tends be acute and can be serious if it spreads to surrounding tissue.

Most of the time an infection of the toenail is due to fungi. The feet are an ideal environment for fungal infections because it is a sweaty area that is often covered with footwear. Fungi thrive in  these warm and moist environments. Even without closed footwear, the nails may still be prone to infections if it is constantly covered with nail polish. A prolonged toenail infection can cause discoloration and deformities of the nails.

Read more on acrylic nail fungi.

Causes and Types of Toenail Infections

There are several microorganisms that can cause toenail infections. However, it is not always just an infection of the nail on its own. The infection may involve the skin around and even underneath the nail. Sometimes the nail itself is not even infected but the surrounding tissue infection is mistaken for a toenail infection.

Fungal Infection of the Toenail

The medical term for fungal infection of the toenail is onychomycosis. It may be isolated to the nail or extend to the surrounding skin around the nail. Most of the time onychomycosis affects the toenail of the big toe or little toes. The infection may be caused by dermatophytes (most common), yeasts or molds.

A dermatophyte infection of the toenail is known as tinea unguium. It mainly occurs when athlete’s foot (tinea) pedis is untreated and then infects the toenail. The main dermatophytes (fungi that can digest keratin) are Trichophyton rubrum and Trichophyton interdigitale.

Read more on toenail fungus.

Less commonly, yeasts can infect the toenail. The main yeast to do so is Candida albicans. It usually starts with a Candida infection of the skin around the nails and of the nail bed. Mold infections of the toenail are uncommon. It is caused by Scopulariopsis brevicaulis and Fusarium species of molds.

Fungal Infection Around the Toenail

The term for a fungal infection of the skin around the nail is known as paronychia. It can be caused to fungi like dermatophytes which may be an extension of a fungal skin infection elsewhere on the feet (athelet’s foot). Fungal paronychia may also occur due to Candida (cutaneous candidiasis) and less commonly due to molds.

Most of the time chronic paronhycia is due to fungi. It can occur on its own withot involving the toenail. If the skin around the nail is injured or damaged, fungi can quickly infiltrate. Candida infection tends to involve the deeper tissue while dermatophytes are limited to the outermost layers of the skin.

Bacterial Infection of the Toenail

Bacteria tend to cause acute infections. A bacterial infection of the toenail itself is uncommon. Most of the times the bacteria cause paronychia – infection of the skin around the toenail. Staphylococci are the main bacteria to cause these infections and is more likely to affect nail biters, with ingrown nails or with other injuries to the nail area. The area around the nail becomes red, swollen and painful. An abscess can form at the site.

Bacterial infections of the toenail are uncommon but can occur if there is damage to the nail, a fungal infection of the nail and in people with weakened immune systems. Usually the infection is of the nail bed. Sometimes these bacterial nail infections causes green discoloration of the nails (chloronychia), like when the bacteria Pseudomonas aeruginosa is involved.

Pictures of Toenail Infection

Some of the pictures below are of infections of the fingernails. However, similar infections occur on the toenails and therefore it appears largely the same.

Athlete's foot with toenail infection

Athlete’s foot with toenail infection



Picture of bacterial paronychia



Picture of Paronychia


Picture of onychomycosis

Picture of onychomycosis



Signs and Symptoms

There may be some degree of variation of the signs and symptoms of a toenail infection, depending on whether it is fungal or bacterial, location (either of the nail or around it) and severity and duration of the infection. The following signs and symptosm may be seen:

  • Rough, cracked or jagged nails.
  • Weak nails that break easily.
  • Powdery nail residue.
  • Yellow, brown, green and even black discoloration of the nails.
  • Thick, twisted and deformed nails.
  • Redness and swelling around toenails.
  • Pain and tenderness along the edges of the nail.
  • Yellow pus discharge, sometimes with oozing and crusting.

Fungi tend to cause chronic infections. As a result there may be discoloration, thickening and erosion of parts of the toenail. These fungal infections do not cause pain until the nail is destroyed to expose the delicate and sensitive nail bed underneath the nail.

Bacteria tend to cause acute infections. Infection of the nail itself by bacteria is not common. Most of the time the skin around the nails and even the nail bed is infected. There is redness, swelling and pain at the area. There may also be a discharge from the site.

It is important to note that there are different disorders of the nail that may present with some of the signs and symptoms above even without an infection. Although toenail infections are usually not considered to be serious, bacterial infections of skin around the nails (paronychia) can lead to complications such as deeper infections (cellutlitis) and the infection can even spread to distant sites.

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