(1) drug rash: some drugs can cause skin allergic reactions, mainly manifested as skin erythema, purpura, blisters and epidermal laxity, itching and pain, sometimes accompanied by low fever. After the rash subsides, there is no hyperpigmentation.

(2) contact dermatitis: refers to the skin contact with certain substances (such as jewelry, bracelets, sandals, cosmetics, etc.), the local occurrence of erythema, edema, itching and pain, and in severe cases, there may be blisters, peeling and other phenomena.

Papules

(3) Eczema: local or generalized erythema, papules, blisters, vesicles, oozing, crusting, desquamation, and hyperpigmentation are visible; intense itching; and there is obvious oozing.

(4) urticaria (hives, rubella): sudden intense itching or burning sensation of the skin; the affected area quickly appeared in different sizes, limited lumpy swollen masses, as small as a grain of rice, as large as the size of the palm of the hand, commonly fingernail to the size of a coin, slightly higher than the surrounding skin.

(5) Itchy skin in cutaneous scratches: scratching with the hand makes a scar.

(6) food allergy: milk, flour, corn, eggs, sugar, tomatoes, potatoes, chocolate, fruits, beef, pork and other foods may cause allergies, food allergies can be a variety of manifestations, the rash is the most common, most often occurring in the face, erythema around the mouth, trunk is also more common, itching and flaking, and can have hyperpigmentation, there are also nausea, diarrhea, abdominal pain.

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(7) environmental factors cause allergies: pollen, mold, dust, trees, tobacco, smoke, perfume, gasoline, paint, insecticides, detergents, drugs, pets, carpets and so on can cause allergies.