What is tinea corporis?
Tinea corporis is a fungal infection of the skin anywhere on body except the areas such as the palms, soles, scalp and groin. Other terms may specifically refer to a fungal infection on these areas, such as tinea capitis (scalp), tinea cruris (groin), tinea barbae (mustache and beard area) and tinea pedis (feet). Tinea corporis is a dermatophyte infection and this type of infection is therefore known as dermatophytosis. All tinea infections are due to dermatophyte fungi, except tinea versicolor which is due to an yeast infection. Tinea corporis is also known as a ringworm of the body because the skin lesions that appear with these fungal infections are round (annular) with raised red borders. It does not involve any type of parasitic worm and the common term, ringworm, can therefore be misleading.
Reasons for Tinea Corporis
The skin is fairly impermeable to most types of infectious microorganisms. It is mainly when the skin is unhealthy or broken that microorganisms may be able to invade it. Tinea infections are superficial fungal infections. This means that it is limited to the outer layers of the skin comprising non-living skin cells. These remnants of cells contain a tough protein known as keratin which covers and protects the more delicate inner living skin layers. Although keratin is resistant to many types of microorganisms, some type of fungi may have specialized enzymes known as keratinases that can digest these outer layers.
There are two main families of fungi that may cause skin infections – dermatophytes and yeasts. Tinea corporis is due to a dermatophyte infection. There are several different species of dermatophytes that may be responsible for tinea corposis. These fungi may also invade the nails in which case the infection is known as tinea unguium. Tinea infections can be transmitted from person-to-person, animal-to-person and in rare cases from the soil to a person.
Some fungal species have a predilection for humans and are transmitted from person-to-person with close contact (anthropophilic fungi). This is more commonly seen between mother and child. Other species have a predilection for animals (zoophilic fungi), particularly domestic pets, and are more likely to be seen with tinea corporis in children. Another risk is through contact with livestock but this is mainly seen in farm workers. Geophilic infections are through contact with soil. Infections can also spread through close contact with non-living objects especially personal items such as towels and combs.
Causes of Tinea Corporis
The common fungal species responsible for tinea corporis includes :
- Trichophyton rubrum
- Trichophyton verrucosum
- Trichophyton mentagrophytes
- Microsporum canis
There are several other dermatophytes that may also be responsible for tinea corporis but overall this is rare. Trichophyton rubrum (T.rubrum) is the most common cause of tinea corporis internationally. T.verrucosum and M.canis may be spread by cattle or domestic pets (cats and dogs) respectively.
Despite being in contact with dermatophytes that could cause a tinea infection, it does not affect every person. There are certain risk factors that increase the chance of developing tinea corporis. This includes :
- Excessive sweating.
- Humid climates.
- Living or working in damp conditions.
- Overcrowded living conditions.
- Having close contact with an infected person and sharing personal items including towels and bed linen.
- Close contact sports.
- People with weak immune systems.
- Wearing very tight clothing.
Signs and Symptoms
Tinea corporis has an incubation period of between 1 to 3 weeks. This means that a person will not experience any symptoms for this period from the time of contracting the infection.
Body Ringworm Rash
- Tinea corporis presents as an itchy skin rash.
- The typical rash is a pink to red slightly raised and scaly rash.
- The center of the rash is usually less red and scaly or may have healed thereby giving a ring-like appearance (annular). Hence the term ringworm.
- The typical rash appears asymmetrical and is more oval than round.
- In some people the rash appears as small circles with no healing in the center thereby resembling small coins (nummular).
- Tiny fluid-filled blisters (pustules) may also be present at times. A large abscess in the middle of the rash surrounded by tiny pustules is known as a kerion.
In certain severe cases particularly in an immune compromised person, the rash may be so extensive and patches continuous that it appears as one large dry and scaly rash especially on the trunk.
Body Ringworm Pictures
Picture of a typical ringworm rash on the body from Wikimedia Commons.
Picture of tinea corporis on the chest from Dermatology Atlas (Brazil) courtesy of Samuel Freire da Silva, M.D. (www.atlasdermatologico.com.br).
Picture of tinea corporis on the abdomen from Dermatology Atlas (Brazil) courtesy of Samuel Freire da Silva, M.D. (www.atlasdermatologico.com.br).
Picture of fungal skin rash from Dermatology Atlas (Brazil) courtesy of Samuel Freire da Silva, M.D. (www.atlasdermatologico.com.br).
Picture of tinea corporis on the limb from Dermatology Atlas (Brazil) courtesy of Samuel Freire da Silva, M.D. (www.atlasdermatologico.com.br).
Picture of tinea corporis on the trunk from Dermatology Atlas (Brazil) courtesy of Samuel Freire da Silva, M.D. (www.atlasdermatologico.com.br).
In most cases tinea corporis does not present with any other symptoms apart from a skin rash. Prolonged infections that are not adequately treated and with constant scratching over a long period of time can lead to discoloration of the skin – usually darkening (hyperpigmentation). The concern however is the development of secondary bacterial infections of the skin which can be severe and quickly lead to serious complications if left untreated. These bacterial infections tend to develop with micro-tears in the skin caused by scratching. The bacteria may be transferred to the site by the fingers or the normal skin bacteria can then infect the site. This leads to symptoms such as :
- Tenderness and then pain as the infection progresses.
- Heat over the affected area.
- Oozing yellow to brown discharge.
- Selling under the skin of the affected area.
Immediate medical attention is necessary at this point.
Diagnosis of Tinea Corporis
Clinical examination is often sufficient to reach a diagnosis. However, sometimes tinea corporis may not always present typically. This can lead to a misdiagnosis with other skin conditions like atopic dermatitis, impetigo amd psoriasis. The diagnosis needs to be made by a dermatologist by one or more of the following methods :
- Skin scrapings are examined microscopically on a potassium hydroxide (KOH) mount.
- Fungal culture where samples are placed on a medium to grow the fungus so that it can be examined.
- Skin biopsy.
Treatment of Tinea Corporis
Tinea corporis can be effectively treated with antifungals. However, it is more difficult to treat and manage in a person who is immune compromised as is the case with poorly controlled diabetes mellitus and HIV/AIDS.
- Topical antifungals (ointments and gels) – terbinafine, clotrimazole, ciclopirox, econazole or butenafine.
- Oral antifungals (tablets and capsules) – terbinafine, fluconazole, itraconazole or griseofulvin.
Corticosteroid creams should not be used as it can mask the symptoms and then worsen it (tinea incognito). Short term use may be considered for very severe symptoms that are causing intense discomfort. Antibacterial ointments may be necessary for bacterial skin infection – this should first be treated along with antibiotics before commencing with antifungal therapy.