Fungal infections of the skin are among the more common types of skin infections. In most cases it is not serious and limited to only the outermost layers of the skin. However, this does not mean that it is any less uncomfortable especially when it occurs on sensitive areas of the body like the groin. The itching can at times be excruciating and embarrassing particularly when scratching the groin area is necessary to ease the discomfort.
What is tinea cruris?
Tinea cruris is the medical term for a fungal skin infection of the groin region. It is also commonly referred to as groin ringworm, jock itch and dhobi itch. The term ringworm is a misnomer as a fungus is not the same organism as a parasitic worm. However, the fact that the common skin fungi (dermatophytes) cause a red ring-like rash has earned it the name ‘ringworm’. The term jock itch has arisen from the prevalence of tinea cruris among athletes whereas a similar prevalence among clothes washers in India known as ‘dhobis’ has led to the name dhobi itch. Other less popular names include groin rot and scrot.
Superficial fungal skin infections like tinea cruris are known as dermatophytosis. It is caused by a type of skin fungi known as dermatophytes. Other type of fungi such as yeasts can also infect the skin but it is not as common as dermatophytes. Groin fungus is among the more common types of dermatophytosis along with athlete’s foot (tinea pedis) and scalp ringworm (tinea capitis). Although tinea cruris occurs globally, it tends to be more frequently seen in hot and humid climates. Men are three times more likely to experience jock itch than women and it tends to affect adults more often than women.
Causes of Tinea Cruris
There are many different species of dermatophytes. Those that are more commonly seen as the cause of tinea cruris include Trichophyton rubrum, Trichophyton tonsurans, Trichophyton mentagrophytes, Trichophyton verrucosum and Epidermophyton floccosum. Studies have shown that T. rubrum may account for as much as 90% of all groin fungal infections. Some species like T. rubrum and E. floccosum often become chronic infections without the inflammatory presentation seen in acute infections, like those caused by T. mentagrophytes.
A groin fungus is often spread from one person to another, usually through sharing personal items like towels. While it is not a common practice, these fungi are very easily transmitted with sharing of underwear or jock straps and should therefore be avoided at all costs. However, another route of transmission is from the feet to the groin. Many of the same fungi that cause athlete’s foot (tinea pedis) also cause tinea cruris. The fungi are easily spread on the hands when a person with athlete’s foot scratches their feet and then touches the groin region.
Fungi tend to thrive in moist, warm and dark areas therefore the groin, like the feet, provide the ideal environment. Dermatophytes have the ability to digest the outer keratinized layers of the skin which is the reason that these fungi are more likely to infect the skin. Despite the environment and enzymes, there are certain risk factors that increase the likelihood of these infections occurring in some people. Tinea cruris is more common in these people:
- Overweight or obese
- Sweat excessively
- Have a weakened immune system or other skin diseases in the area
- Staying in wet clothes for long periods
- Wear tight underwear
- Live in tropical climates
Signs and Symptoms
Tinea cruris typically presents as an itchy rash. Some species of fungi that cause this groin infection may trigger extensive inflammation, while others may present with a non-inflammatory itchy groin rash. It most commonly occurs on the crease between the trunk and thighs. The area may be red to dark brown in color, with the latter occurring usually as a result of persistent scratching. The skin texture may also change over time. The borders of the affected region may be lined with small blisters.
Apart from itching, there may also be complaints of tingling and burning which is worse on hot days and with wearing tight underwear.The skin of the affected area also dries up excessively and peels. Often there are is a powdery residue with scratching which is the peeling skin. Many people often complain of moisture in the area which has a musty odor although this may also be present in the absence of any rash. Excessive or vigorous scratching can lead to cuts in the skin and there may be pain and burning as a result.
Tests for Diagnosis
In most cases the diagnosis of tinea cruris can be reached with macroscopic examination of the area. However, if additional tests are required then it may involve:
- Collecting skin scrapings from the affected area, performing a KOH wet mount and examining the slide under a microscope.
- Using a sample from the area to grow a fungal culture in the laboratory for further examination.
Sometimes tinea cruris is incorrectly diagnosed. Non-responsiveness to treatment may require further procedures like examining the area under a Wood lamp or performing a punch biopsy for microscopic evaluation.
Treatment and Prevention
Fungal infections of the skin tend to be persistent and require medical treatment. While milder cases may be effectively treated with over-the-counter (OTC) antifungals. This may include a range of topical applications including ointments, powders and spray. However, more persistent infections may not resolve although there may be initial signs of improvement. In these cases prescription medication is usually necessary, often a combination of oral and topical medication.
These prescription drugs include:
In addition, topical corticosteroid ointments may also be prescribed in some instances to reduce extensive inflammation of the affected area. Treatment may need to be continued for up to 30 days after the symptoms subside, especially in long standing cases. Tinea pedis (athlete’s foot) should be treated simultaneously if present. Due to the high rate of recurrence, it is important for patients to understand how the groin fungus is spread and thrives in order to avoid a new infection. These measures may include:
- Treat athlete’s foot or fungal skin infections elsewhere on the body immediately once identified.
- Opt for loose fitting underwear like boxer shorts for men instead of briefs.
- Underwear should be made of light airy fabrics.
- Always wipe the groin region thoroughly after bathing.
- Use drying powders in the groin region if there is excessive sweating.