Two weeks before the holiday, 58-year-old Wang Da-ma went to a barber store near her home to have her gray hair dyed black. When she was done, looking at herself in the mirror, Mrs. Wang was very satisfied. But home only after half a day, her scalp is more and more itchy, a look, long a piece of red spots, pimples, and blisters. Really itchy, Wang can not help but scratch, this is bad, the blisters broke. Seeing this situation, Wang Auntie rushed to the city hospital dermatology, please doctor to see. The result of the diagnosis and treatment is: hair dye dermatitis. This is a typical allergic dermatitis caused by hair coloring. Allergic dermatitis, also known as allergic dermatitis, is an inflammatory reaction of the skin caused by a number of factors, including allergens (allergens) through the mechanism of allergic reactions. Allergic dermatitis is the most common disease in dermatology. With modernization and environmental changes, exposure to chemicals is increasing, making the chances of people suffering from allergic dermatitis significantly higher. Common clinical allergic dermatitis includes contact dermatitis, hair dye dermatitis, eczema and so on. The allergic reactions caused by different pathogenic factors are different. First, the development of atopic dermatitis internal and external factors The cause of atopic dermatitis is very complex, and its development is related to internal and external factors. The internal factor is the patient’s own “allergy”, that is, very sensitive to external stimuli, which plays a dominant role in the development of atopic dermatitis, the patient sometimes can not tolerate to the normal person is harmless stimuli. The instability of the internal environment, such as chronic digestive diseases, mental stress, insomnia, excessive fatigue, emotional changes and other mental changes, as well as infected lesions, metabolic disorders and endocrine dysfunction, etc., can induce or aggravate the condition of atopic dermatitis. There are also many external factors, including diet, inhalants, climate, contact with allergens and other factors. Among them, seafood, spicy food, alcohol, inhalation of pollen, dust mites, cold weather, contact with chemicals, soaps and detergents are the most common triggers of atopic dermatitis. Due to such complex reasons, it makes atopic dermatitis recurring due to the interweaving of numerous causes and triggering factors. Second, the common characteristics of allergic dermatitis Fundamental characteristics: allergic dermatitis is the causative factor through the body’s immune system of the perverse reaction in the skin damage, seize this point, it is easy to identify with the name of close or similar dermatitis. There is a sensitization process: from the stimulus that is the allergen used in the human body, to the skin lesions, there is a period of time, most of the first time does not develop, the second time after the onset of the disease, which is the immune system brewing the results of perverse reactions. Family genetic characteristics: the proportion of families with a history of urticaria, asthma or allergic rhinitis and other genetic allergies is high. Both parents have a history of genetic allergies, and their children have a higher chance of developing atopic dermatitis. Therefore, when you find that your child has dermatitis, you should check the history of allergies in your family. Characterized by recurrent episodes: most of them recur after contact with the allergen, but sometimes the allergen is not obvious and should be carefully traced. Third, the clinical manifestations and diagnostic methods of common allergic dermatitis 1, contact dermatitis is due to the skin mucous membrane contact with certain substances, in the contact area of acute skin inflammatory reaction . The cause can be divided into primary stimulation and metabolic reaction. Clinical manifestations of erythema, blisters, blisters and even necrosis, etc., the site and scope of lesions and contact with the contact area of the contact material contact, clear boundaries, the course of the disease has a self-limiting. 2, eczema is a kind of skin inflammatory disease with obvious exudation tendency caused by many internal and external factors, the cause is complex, generally not easy to find, the clinical process is mostly chronic, alternating between improvement and aggravation. Eczema rash pattern is diversified, the acute stage manifests as erythema, papule, papule herpes, accompanied by edema, severe cases can appear blisters oozing, there can be scratches, scabs; chronic cases have limited infiltration and hypertrophy. The itching is intense and easy to recur. According to its clinical manifestations are divided into acute, subacute, chronic three. Fourth, the therapeutic countermeasures of atopic dermatitis 1, the therapeutic goal of atopic dermatitis Control skin inflammation as soon as possible, relieve itching, improve and enhance the quality of life of patients by delaying and reducing the attacks. 2.General principles of preventing atopic dermatitis The causes of the disease should be searched for and eliminated and avoided as much as possible. (1) Reduce the aggravating factors and stimulating factors: such as mechanical factors (scratching, friction); physical and chemical factors (hot water, high temperature, low humidity, irritating drugs); biological factors (plants and animals, microbial infections, etc.); mental tension or emotional depression or digestive disorders. (2) Keep away from allergenic factors: this is the most fundamental way to prevent atopic dermatitis. Minimize environmental allergens, such as inhalant allergens (all substances that can be inhaled through the respiratory tract are potential allergens), including dust, dust mites, cotton wool, pollen (spring, summer and fall), animal hair, fungi, insects and smoke. Food allergens (are allergens that cause allergic reactions through ingestion), including fish, shrimp, crab, beef and lamb, eggs, milk, peanuts, soybeans and nuts. Contact allergens (allergens that trigger allergic reactions through contact with the skin or mucous membranes), including clothing, dyes, cosmetics, jewelry, topical medications, lacquers, organic solvents, hair dyes and disinfectants. In order to create a healthy and hygienic environment, it is important to maintain indoor hygiene, open windows for ventilation, maintain appropriate temperature and humidity, and not to use disinfectants casually; minimize children’s exposure to pollen in spring; avoid direct sunlight in summer; do not keep pets in the house, especially not indoors; use carpets sparingly; vacuum regularly; do not use electric blankets; and avoid irritating cosmetics. (3) take care of the skin: scientific and reasonable bathing, choose the pH (PH) neutral, non-irritating soap; not indiscriminate use of skin care products, underwear to choose soft cotton fabrics, should not wear wool, synthetic fabrics, these fabrics are rough, and skin irritation, easy to trigger dermatitis, eczema. (4) pay attention to diet, balanced nutrition: eat more fruits, vegetables and other vitamin-rich foods, vitamin C is a natural antihistamine, should be taken from the diet every day. Eat less fish and shrimp, beef and mutton and greasy, sweet and stimulating foods.