Fungal infections can be superficial, subcutaneous or systemic, and the site of infection depends on the characteristics of the fungus and the status of the host. Superficial fungal infections usually occur in the cuticle, hair and finger (toe) nails. Superficial fungal infections can be classified as superficial fungal infections that cause an inflammatory response (such as ringworm, ringworm, tinea pedis, ringworm, etc.) or superficial fungal infections that do not cause or cause less inflammatory response (such as axillary hair infection caused by Trichophyton rubrum) according to whether they cause an inflammatory response. 1. Causes and modes of transmission of dermatophytosis Dermatophytosis is a superficial fungal infection caused by three major groups of fungi that can invade and colonize keratinized tissues (hair, skin, and nails). These fungi, collectively known as dermatophytes, are very similar in physiology, morphology, and pathogenicity and include the genera Tinea superficialis, Microsporum, and Trichophyton. Species of these three fungal groups that do not invade human and animal keratinized tissues are not included. The common dermatophytes include 10 species, and 20 other fungi can occasionally be obtained by culture. The 10 common dermatophytes are: Trichophyton spp. Protozoal: Trichophyton spp. Interdigital: Trichophyton spp. Interdigital: Trichophyton rubrum Prohuman: Trichophyton rubrum prohumanum Prohuman: Trichophyton verrucosum Prohuman: Microsporum spp. Microsporum canis Prohuman: Microsporum ferrugineum Prohuman: Microsporum plasterum Prohuman: Microsporum epidermidis Prohuman: Trichophyton flocculare Pro-human: Ringworm and ringworm can be transmitted from human to human, animal to human, and soil to human, each with typical characteristics. Soil-friendly fungi are present in soil and infect humans only sporadically, often due to direct contact with soil. Microsporum gypsum is the most common hyphophilic fungus cultured from patients with tinea corporis and ringworm, and is more virulent than other hyphophilic fungi. Soil-loving dermatophytosis often causes a moderate inflammatory response. Some of the fungi that cause dermatophytosis are zoophilic. Some pets (dogs and cats, etc.) in cities are a common source of dermatophytosis and. Direct contact with animals can cause direct infection, and indirect infection can be caused by animal fur carried on clothing, present indoors or in food. Exposed areas such as the scalp, beard, face, and upper extremities are easy areas for infection. Pro-animal dermatophytosis often causes a strong inflammatory response (may have pustules and blisters). Pro-animal fungi are transmitted through direct person-to-person contact or through contact with contaminants. Kindred dermatophytoses can cause either a mild or no inflammatory response in general or a strong inflammatory response, which when it occurs can lead to pustules or other inflammatory manifestations. A non-inflammatory, proximate fungal infection can leave the infected individual in a resting “carrier” state, delaying clinical diagnosis, but can lead to the spread of the fungal infection. The occurrence and severity of dermatophytosis is related to a number of factors: the immune status of the body: patients with impaired immunity are susceptible to severe or refractory fungal infections. With the advances in chemotherapy and transplant medicine, certain non-pathogenic fungi can become pathogenic, resulting in an increased chance of opportunistic fungal infections. patients with HIV only cause an increase in the severity of dermatophytosis and do not increase the probability of developing dermatophytosis. There is no evidence that diabetic patients are susceptible to dermatophyte infections; however, diabetes can affect the course of dermatophyte infections (longer duration). Age: Dermatophytosis often occurs after puberty (except for ringworm of the head). Risk factors for dermatophyte infections before puberty include home exposure to tinea capitis and tinea pedis, and some environmental factors include contamination from hats, brushes, and haircutting equipment. Gender: Tinea capitis infections are about five times more common in males than in females. Tinea pedis and ringworm are more common in males than in females. After puberty, males are also more likely to develop ringworm of the nail than females. However, ringworm of the head caused by Trichophyton cutaneum is more common in female adult patients than in male adult patients. Department: Sebum has an inhibitory effect on dermatophytes and the activity of the disease may be related to the number and activity of sebaceous glands in a particular area. Lack of sebaceous glands is an important pathogenic factor in the development of tinea pedis. Lifestyle habits: Wearing closed shoes significantly increases the probability of developing tinea pedis and tinea nail. Skin barrier: A disrupted skin barrier or skin maceration is more conducive to dermatophyte invasion. 2. Causes of common dermatophytoses: (1) Tinea corporis: Tinea corporis refers to dermatophyte infections that occur on areas other than the scalp, hair, palmoplantar and nails. It is mainly caused by infections with Trichophyton rubrum, Trichophyton rubrum, Microsporum canis, and Trichophyton rubrum. It can be transmitted directly by contact with infected patients or animals; by contact with contaminants; and by self-inoculation due to colonization of the dermatophytes on the foot. Pediatric patients are more likely to be infected by contact with animals that are pro-animal fungi, such as microsporum canis from cats or dogs. Tight-fitting clothing and hot and humid climates are often associated with the development of ringworm. Occupational or recreational exposure (e.g., dormitories, gyms, locker rooms, outdoor work, fighting) is an important susceptibility factor. (2) Tinea corporis: Tinea corporis refers to ringworm infections of the skin in the groin, perineum, perianal area, and buttocks, and is part of ringworm that occurs in specific areas of the body and accounts for the second most common form of dermatophytosis. It is mainly caused by Trichophyton rubrum and Trichophyton flocculare, but also by Trichophyton spp. and Trichophyton verrucosum. It is caused by direct infection from contact with infected patients or through contact with contaminants, or by inoculation of foot fungus colonization itself. (3) Tinea capitis: Tinea capitis is the most common dermatophytosis. Tinea capitis refers to infections caused by dermatophytes that invade the smooth skin between the fingers, palms, and sides of the palms, and tinea pedis is a dermatophyte infection between the toes, plantar, heel, and lateral edges of the feet. It is mainly caused by Trichophyton rubrum, Trichophyton spp. and Flocculina epidermidis. Closed shoes will increase the chance of infection, and public baths, swimming pools, etc. will increase the chance of infection. 3, summer characteristics fungus like warm and humid, the optimal growth temperature 22 ℃ ~ 36 ℃, relative humidity 95% ~ 100%. In summer, fungi often multiply faster, and summer hands and feet and body folds are often sweaty and humid, so if they are not wiped clean and kept dry in time, they can easily become infected with fungi and develop ringworm. 4. Treatment (1) Tinea corporis and ringworm: Topical treatment is preferred, and commonly used imidazole drugs include 1% bifenazole, 2% miconazole, 1-3% clotrimazole, 2% ketoconazole, 1% econazole, 2% sertaconazole, etc.; arylamines include 1% naftifine, 1% terbinafine, or 1% butenafine preparations; others include 2.5% amorolfine, 1% ciclopirox, 2% liranafil, etc. Different dosage forms are used according to the clinical type, topical application twice a day, and the course of treatment is 2~4 weeks. Oral antifungal drug treatment is suitable for extensive or inflammatory lesions. Commonly used drugs are fluconazole 150mg, 1 time/week for 4-6 weeks; itraconazole, 100mg, 1 time/day for 15 days; and terbinafine, 250mg, 1 time/day for 2 weeks. (2) Tinea pedis and tinea pedis: Mild interdigital tinea pedis can be treated with topical medications such as allyamine, azole, ciclopirox, benzylamine, tolnaftate, and undecenoic acid. Keratosis pilaris can be treated with additional keratin exfoliators such as urea, salicylic acid, or lactic acid preparations. Severe or refractory tinea pedis can be treated with oral antifungal medications. Commonly used medications are terbinafine 250mg once daily for 2 weeks, itraconazole 200mg twice daily for 2 weeks, or 200mg once daily for 3 weeks, or 100mg once daily for 4 weeks. Fluconazole 150mg, 1 time/week for 3-4 weeks; or Fluconazole 50mg, 1 time/day for 30 days. If combined with nail fungus, treat the nail fungus to prevent the recurrence of tinea pedis. If tinea pedis occurs with maceration, exfoliation, or malodor, Gram stain or bacterial culture should be used to look for the presence of bacterial co-infection. After bacterial infection is confirmed, antibiotic treatment should be used. Blistering-herpetic tinea pedis is caused by a T-cell-mediated immune response, and symptomatic treatment with topical glucocorticoids should be taken along with initiation of antifungal drug therapy. 5. Preventive and relapse prevention measures: (1) Tinea corporis and tinea corporis: Avoid close contact with other patients and animals with fungal infections; avoid indirect contact with towels and bath tubs used by patients; wear loose clothing; dry well after bathing; lose weight (if you are obese); wash and iron contaminated clothing and bed linen; use topical dispersions; treat tinea capitis, tinea nail and tinea capitis actively if the patient has them. (2) Tinea capitis: pay attention to personal hygiene and keep the feet dry regularly; do not share towels, bath towels, slippers, etc., and disinfect footbaths and bathtubs regularly; change socks regularly and do not wash them with other people’s to avoid cross-infection; treat tinea capitis in other members of the family at the same time.