Itchy arm skin with small bumps may be related to contact dermatitis, self-sensitized eczema, perioral keratosis, insect bite dermatitis and drug rash. 1. Contact dermatitis: patients contact with external allergens cause erythema, papules and blisters, patients have obvious itching. Patients should get away from the allergens in time, patients can be under the guidance of the doctor, external fluoride ointment, betamethasone cream and so on. 2. Auto-sensitized eczema: its cause may be related to the environment, diet, spirit, there will be double upper extremity papules, accompanied by red bumps and itching. Patients can take loratadine as prescribed by the doctor. 3. Perioral keratosis: it may be related to heredity and other factors, mainly in the extensor side or lateral side of the limbs, with small pimples centered on hair follicles, which are relatively rough to touch, affecting the aesthetic appearance, and can be consulted by dermatologists. 4. Insect bite dermatitis: because mosquito bites will release a venom, resulting in itchy skin on both upper limbs, erythematous papules. Patients can be under the guidance of the doctor, external application of compound beclomethasone camphor cream, glycerite, if the patient itching symptoms are more serious, you can also take loratadine, benadryl and so on. 5. Drug rash: due to oral antibiotics or other drugs caused by drug allergies, itchy bumps appear on the skin of both upper limbs. Patients should immediately stop using allergenic drugs, if the skin lesions appear oozing, you can make local wet compresses.