Many patients with skin diseases are very concerned about whether their skin disease is contagious when they visit the clinic, but in fact, contagious skin disease types only account for a small percentage of skin diseases. Direct contact transmission is through direct contact with the skin, blood, body fluids and secretions (such as sputum, feces, saliva, urine, exudate, etc.) of patients or sick animals and infectious, indirect contact transmission is through the patient’s contaminated utensils (such as tableware, clothing, bedding, toiletries, shoes, hats, towels, etc.) and infectious. This is because the human body has a certain immunity, and only when the immunity decreases, such as in weakness, chronic internal diseases, long-term use of immunosuppressants and hormones, tumors and other conditions, the chance of being infected will greatly increase. I. Which skin diseases are contagious? Infectious skin diseases include: herpes simplex, chickenpox, genital herpes, Kaposi’s chickenpox-like rash, infectious mononucleosis, smallpox, B virus disease, bovine pox, milking human nodules, sheep pox, infectious molluscum contagiosum, common warts, flat warts, measles, atypical measles syndrome, hand, foot and mouth disease, respiratory syncytial virus infection, foot and mouth disease, infectious erythema, early childhood emergency rash, venereal lymphogranuloma Parrot fever, typhus, impetigo, scarlet fever, gonorrhea, non-gonococcal urethritis, desert sores, leprosy, skin tuberculosis, rhinophyma, brucellosis, plague, soft chancre, anthrax, cutaneous diphtheria, ringworm, ringworm, tinea capitis, ringworm, ringworm nail, ringworm, ringworm, syphilis, AIDS, yaws, pinta, cutaneous black fever, trichomoniasis, malaria, pubic lice, scabies, etc. Second, which skin diseases are hereditary? Hereditary dermatoses account for a large proportion of dermatoses and are dermatoses caused by disease-causing mutations, which obey the general law of heredity, i.e. patients appear in a certain number of proportions in their grandparents and offspring, and are only passed vertically between the upper and lower generations of the family, without involving unrelated individuals in the family. There are four types of inheritance for hereditary skin diseases as follows: 1. Autosomal dominant inheritance: these skin diseases are characterized by at least one of the two parents being a patient and at least half of the children having the disease, independent of gender, and the condition is mostly not serious and does not affect life and work ability. Autosomal dominant dermatoses account for about 70% of hereditary dermatoses, the common ones are: common ichthyosis, callus formation, hair follicle keratosis, sweaty ectodermal dysplasia, A Bin syndrome, vasodilatation, familial chronic benign aspergillosis, albinism, red furunculosis, herpetic epidermolysis bullosa simplex, pigment incontinence, sweat duct keratosis, sebaceous adenoma, freckles, hair epithelioma, neurofibromatosis, white frontal hair, congenital thick nail disease, etc. 2, autosomal recessive inheritance: these skin diseases have two normal parents, but their siblings may have the disease, the incidence of family members of both parents is high, do not see consecutive generations of inheritance, the patient’s physical and intellectual development is obviously impaired, poor life prognosis and other characteristics. Common autosomal recessive dermatoses include: albinism, congenital ichthyosis, stained dry skin disease, congenital porphyria, lipoprotein-like deposition, hemochromatosis, congenital nail deficiency, elastic fiber pseudoxanthoma, enteropathic acrodermatitis, skin fatty deposits, congenital closed sweating ectodermal dysplasia, etc. 3, sex-linked inheritance: these dermatoses have more men than women, intergenerational inheritance, all sons born to female patients have the disease, and the father of female patients must be symptomatic patients and other characteristics. The common sex-linked hereditary skin diseases include: sex-linked hereditary ichthyosis, congenital ectodermal dysplasia, congenital dyskeratosis, diffuse body angiokeratoma, atrophic pore keratosis, etc. 4.Polygenic inheritance: This kind of skin disease refers to the inheritance mode in which the genetic characteristics are not determined by a pair of genes, but by several pairs of genes, which are influenced by environmental factors, and the incidence rate in families is significantly higher than that of the general group. Polygenic hereditary skin diseases are common: seborrheic dermatitis, acne vulgaris, lupus erythematosus, psoriasis, hirsutism, baldness, etc. Third, which skin diseases need to avoid eating? Many dermatology patients ask their doctors if they need to avoid eating after a consultation. Indeed, there are many clinical skin diseases that require dietary modification and avoidance. Such as eczema, urticaria, atopic dermatitis, neurodermatitis, psoriasis, pityriasis rosea, lichen planus, erythrodermatitis, seborrheic dermatitis and other common diseases, the onset of its diet has a very close relationship, can eat irritating food or hair and aggravate the disease, so for those patients with food allergies, during the onset or after the disease is cured, should be limited or prohibited to eat fish, shrimp, crab, sheep and other fishy Therefore, for those patients who have food allergies, during the onset or after the disease has healed, they should limit or prohibit the consumption of fish, shrimp, crab, goat and other fishy things, chicken, duck, goose and other poultry food, as well as onion, ginger, garlic, chili, coriander, alcohol and other stimulating food or fried and other indigestible food. Fourth, which skin diseases are more likely to occur in the elderly? The onset of many skin diseases has a certain relationship with age, as the elderly age, the physiological structure of the skin gradually degenerative changes, barrier resistance and other physiological functions are gradually reduced, so there are a number of skin diseases in the elderly, the common ones are: postherpetic neuralgia, filiform warts, chronic recurrent dermatitis, pollicization, hyperkeratosis ringworm, light keratosis, hand and foot chaps, cracked eczema, pruritus, ventral lateral dermatomal neuritis, menopausal keratoderma, verrucous dyskeratoma, persistent bean-like hyperkeratosis, sclerosing atrophic lichen planus, aspergillosis, herpes-like aspergillosis, herpetiform aspergillosis, scarring aspergillosis, herpes-like dermatitis, acquired herpetic epidermolysis bullosa, transient acantholytic dermatosis, subkeratotic pustular dermatosis, skin laxity, eyelid laxity, nodular elastosis, senile skin atrophy, nodular vasculitis, lymphoma-like granulomatosis, progressive pigmented purpuric dermatosis, erythema limbicum, traumatic fat necrosis, sebaceous deficiency, facial xanthoma, progressive necrotizing yellow granuloma, primary systemic amyloidosis, diabetic dermatosis, senile leukoplakia, senile female genital atrophy, seborrheic keratosis, sebaceous nevus, senile sebaceous gland carcinoma, soft fibroma, Kaposi’s sarcoma, lymphangioleiomyosarcoma, lipoma, spindle cell lipoma, liposarcoma, non-Hodgkin’s lymphoma, etc. V. What skin diseases are more common in young people? There is often a relationship between the onset of many skin diseases and age, and certain diseases are likely to occur in certain age groups. The common skin diseases that occur in young people are: genital herpes, bull pox, sheep pox, milking man nodules, lichen planus, atypical measles syndrome, condyloma acuminata, venereal lymphogranuloma, whiskers, balding folliculitis, scarring folliculitis, abscess perifolliculitis, necrotizing acne, carbuncle, purulent sweat gland infection, facial pyoderma, gonorrhea, non-gonococcal urethritis, scleroderma, molluscum contagiosum, soft chancre. Erythema nodosum, soft chancre, syphilis, yaws, pinta, cutaneous black fever, trichomoniasis, pubic lice, hunting reaction, trench foot, polymorphic heliotrope, phyto-heliotrope, mud snail-heliotrope, juvenile spring rash, surfers’ nodules, lupus erythematosus, Leukocerebrosider’s syndrome, neurodermatitis, simple itchy rash, artificial dermatitis, idiopathic late-onset immunoglobulin deficiency, tinea capitis, eosinophilic acid pustular folliculitis, follicular keratosis, punctate palmoplantar keratosis, erythema multiforme, pityriasis rosea, lichen planus, pubertal atrophy striae, erythema nodosum, extremity cyanosis, reticulocutaneous cyanosis, Raynaud’s disease, occlusive thrombophlebitis, subcutaneous adipose granuloma, nodular febrile nonsuppurative seborrhea, seborrhea, seborrheic dermatitis, acne vulgaris, rosacea, perioral dermatitis, fox, baldness, Seborrheic alopecia, generalized hirsutism, contact labyrinthitis, exfoliative labyrinthitis, epidermal nevus, etc. Sixth, which skin diseases are more likely to occur in women? Many skin diseases have a certain relationship with gender, because of certain physiological structures and functions unique to women, clinically there are many skin diseases that are specific to women and are more likely to occur in women. Some of the most common ones are: female vaginal candidiasis, facial pyoderma, common lupus, hard erythema, acute female vaginal ulcer, genitourinary trichomoniasis, itchy rash of pregnancy, erythema multiforme, telecentric annular erythema, erythema simplex, erythema nodosum, oily dermatitis, polymorphic heliotrope, phyto-heliotrope, mud snail heliotrope, facial reoccurring dermatitis, exudative neurodermatitis, artificial dermatitis, skin neuralgia, nodular itchy rash, sclerosing atrophic lichen planus, lupus erythematosus, scleroderma, dry syndrome, mixed connective tissue disease, gestational herpes, gestational papular dermatitis, palmoplantar pustulosis, anterior tibial mucinous edema, painful obesity, granuloma annulare, lipoid progressive necrosis, polymorphic granuloma, chloasma, perioral dermatitis, acute febrile neutrophilic dermatitis, urticarial vasculitis, erythrocyanosis, lipo membranitis, necrolytic relaxed wandering erythema, menstrual rash, anemic nevus, mondo disease, allergic granulomatosis, leucoderma, reticulocytosis, segmental hyaline vasculitis, Raynaud’s disease, cutaneous allergic nodular vasculitis, verrucous acanthosis, progressive metacarpal keratosis, menopausal keratosis, mottled atrophy, stretch marks, female hirsutism, exfoliative labyrinthitis, aphthous stomatitis, leukoplakia, female vaginal ulcers The following are some examples of these diseases: female vaginal atrophy, sweat duct tumor, atrophic polychondritis, frictional melanosis, pigmentary incontinence, focal dermal hypoplasia, acromegaly, polymastia, and polypituitis.