Understanding Ringworm (Tinea Corporis)

The Ring-shaped Skin Infection Not Caused by a Worm

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Ringworm, also known as tinea, is not caused by a worm as the name suggests. It is a contagious fungal infection caused by mold-like parasites that live on the outer layer of the skin.

Tinea corporis broadly refers to ringworm infections that appear predominately on the legs or arms but can manifest on any part of the body. Tinea capitis, by contrast, is an infection specifically of the scalp, although it can affect any part of the head or face that has hair shafts and follicles (such as the beard, eyelashes, or eyebrows).

Ringworm is a classified as a dermatophytic infection. Dermatophytes are a group of fungi that infect and survive on dead keratin (the top layer of the epidermis). The fungi most associated with the condition are Trichophyton rubrum, Microsporum canis, and Trichophyton mentagrophytes.

Causes

Ringworm is caused by a fungus that lives on the dead tissues of hair, skin, and nails. They thrive in warm, moist areas of the body and are commonly seen in tropical and subtropical climates. It affects men and women of all ages in equal part, although it is more common in children.

There are several factors that can increase the risk of ringworm:

  • lack of hygiene
  • having damp skin for extended periods of time (including sweat)
  • minor skin and nail injuries
  • close physical contact with others

Ringworm is highly contagious and can be easily spread by coming in close contact with someone else's body. It can also be passed by touching objects or surfaces contaminated with the fungus, including combs, pool surfaces, towels, doorknobs, bedding, showers, soil, and pets.

Signs and Symptoms

The most common appearance of ringworm is a lesion that begins as a flat, scaly spot that gradually develops a raised border and advances outward into a circular ring shape. The border is usually raised and scaly while the central area is typically flat with fine scaling.

The rash can appear anywhere on the body and is often itchy.

Some infections, especially those treated with a topical steroid like hydrocortisone, can have vesicles or pustules on the border or the center of the lesion.

Diagnosis

Ringworm infection is pretty self-apparent, given its unmistakable appearance. However, ringworm can sometimes mimic other skin conditions, including granuloma annulare, eczema, and tinea versicolor. The same can be said for infections of the scalp, which are often hard to distinguish from psoriasis or seborrheic dermatitis.

Your primary care physician or dermatologist will likely be able to tell the difference based on appearance, although a KOH test will often be used to provide more definitive proof. (By contrast, fungal cultures are rarely used as treatment remains more-or-less the same irrespective of fungal type).

Treatment

Topical Creams

Ringworm typically responds well to topical antifungals, which are applied to lesions twice daily for at least three weeks. While lesions tend to clear up within two weeks, treatment should be continued for another week to ensure the fungus is completely eradicated.

Topical creams can be purchased over-the-counter or prescribed by your doctor. When using a topical cream, wash and dry the affected areas before applying the cream.

Be sure to wash hands thoroughly following application. Do not apply a bandage over the rash.

The most commonly prescribed topical anti-fungal creams are:

  • Monistic (miconazole)
  • Mycelex (clotrimazole)
  • Nizoral (ketoconazole)
  • Lamisil (terbinafine)

Oral Medications

Oral medications are rarely indicated but may be used if an infection is serious or extensive. When prescribed, the drugs are taken once daily for seven days and offer a cure rate of around 100 percent.

Recommended oral antifungals include:

  • Terbinafine (Lamisil) 250 mg
  • Itraconazole (Sporanox) 200 mg

Prevention

Because fungi prefer warm, moist environments, always keep your skin dry and clean, especially if living in tropical or subtropical climates.

You can also reduce ringworm risk by following a few simple tips:

  • maintain proper hygiene, particularly when playing contact sports
  • wash your hands after touching animals, soil, or plants
  • avoid coming into contact with ringworm lesions on others
  • wear loose-fitting clothes in humid weather
  • keep bathtubs, showers, and sinks clean and sanitized

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