When raising cats and dogs, you should be careful about infection with tinea corporis and cruris. How to treat tinea corporis and cruris?

Author: Wang Aiping, Chief Physician, Peking University First Hospital

Deputy Director of the Dermatomycology Group of the Chinese Society of Dermatology and Venereology

Reviewer: Chen Yong, Chief Physician, Beijing Chaoyang Hospital, Capital Medical University

Tinea corporis is a superficial skin infection caused by dermatophytes. Dermatophytes are keratinophilic and the skin has keratin components, so it can be invaded by dermatophytes.

Tinea corporis generally refers to dermatophyte infections that occur on smooth skin. The inner thigh root area also has smooth skin, but because it is close to the external genitalia and the location is relatively special, it is mentioned separately and named tinea cruris, which specifically refers to dermatophyte infections that occur on the inner thigh root and buttocks.

Tinea cruris is a special type of tinea corporis.

1. How do you get tinea corporis and cruris?

There are two sources of infection with tinea corporis.

One is self-inoculation. For example, if you have tinea pedis (commonly known as athlete's foot), scratching your feet and then scratching the smooth skin of other parts of your body will cause tinea corporis, which is relatively less contagious. Tinea cruris is mostly caused by self-inoculation of athlete's foot.

The second is from animals. For example, cats and dogs at home have ringworm, and contact with cats and dogs leads to infection. Ringworm caused by animal dermatophytes is clearly contagious and can be easily transmitted to others.

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Dermatophytes prefer warm and humid environments. In the summer, when the temperature is high and humidity is high, tinea corporis and tinea cruris are more likely to occur, so special attention should be paid. Tinea cruris is especially common because the thighs are warm and humid, which is conducive to the growth of dermatophytes. People who sweat easily or are obese are more likely to get tinea cruris.

Young adults are more likely to get athlete's foot and, through self-inoculation, are also more likely to get tinea corporis. Children are more likely to like cats and dogs and are also more likely to get tinea corporis.

2. What are the clinical manifestations of tinea corporis and cruris?

Tinea corporis is commonly known as "ringworm". The coin-like ring-shaped lesions are a very important feature of tinea corporis. Tinea corporis starts as a small red bump, which gradually expands from the center to the periphery over time, forming a ring-shaped lesion.

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Tinea corporis is usually accompanied by itching. Of course, the degree of itching varies from person to person. Some people feel it is mild, while others feel it is very severe.

Tinea cruris usually appears as annular or semi-circular lesions on the inner side of the thigh root, which gradually expand from the inside to the outside and may affect the buttocks, accompanied by itching, which can be unilateral or bilateral.

Tinea corporis and tinea cruris can occur at the same time, which is a generalized tinea corporis and tinea cruris. For example, if you have very severe athlete's foot and do not treat it properly, in the summer and autumn, when the environment is warm and humid, and you do not pay much attention to personal hygiene, it is easy to cause tinea corporis and tinea cruris.

If you take glucocorticoids and other drugs that reduce the body's immunity at the same time, it can cause widespread tinea corporis and cruris. Or if you are infected with tinea corporis and think it is dermatitis or eczema, and then use some glucocorticoid ointments externally, it may cause widespread tinea corporis and cruris.

3. How to diagnose tinea corporis and cruris?

Tinea corporis and tinea cruris have a very characteristic clinical manifestation. Annular, semi-circular, or clearly-bounded erythema can be seen on smooth skin, and some scales may appear. This situation may be tinea corporis or tinea cruris.

How to diagnose?

You can do a fungal examination, scrape some skin scales and put them under a microscope. If you can see fungal components under the microscope, you can confirm the diagnosis.

Tinea corporis and tinea cruris can affect the patient's quality of life. Some cases of tinea corporis and tinea cruris are contagious, so it is necessary to actively treat them. Tinea cruris usually comes from athlete's foot, so when treating tinea cruris, you must also treat athlete's foot at the same time, otherwise tinea cruris will be difficult to cure. In addition, animals must be effectively managed and treated, otherwise tinea corporis will never be cured.

4. How to treat tinea corporis and cruris?

Dermatophytes invade the outermost stratum corneum of the skin, so the first choice for tinea corporis and cruris is to use topical drugs. Commonly used topical antifungal drugs in clinical practice can be selected, such as imidazole drugs, such as miconazole, ketoconazole, etc.; allylamine drugs, such as terbinafine, naftifine, etc. Apply 1 to 2 times a day, and the application area should be larger than the skin lesions. It can basically be cured in 2 to 4 weeks.

It should be emphasized that highly irritating drugs should not be used on the groin area, especially drugs containing alcohol and acid, as they can easily cause irritant dermatitis.