Children with bumps on their arms are considered to be insect bite dermatitis, eczema, hives and so on. 1. Insect bite dermatitis: this condition is common in the summer, if there are mosquitoes or other insects in the living environment, there will be an allergic reaction after being bitten, manifested as bumps, usually accompanied by itching symptoms. 2. Perifollicular keratosis: this is a chronic follicular keratosis dermatosis, will be in the upper arm, thigh extensor parts of the symmetrical distribution of needle tip to corn size follicular pimples, pimples for the color of the skin, do not blend, the tip of the light brown keratin plugs, and autosomal dominant inheritance, vitamin A deficiency metabolic disorders related. 3. Erythematous furuncle: This is a follicular intertriginous papule that appears on the sides of the limbs and trunk, with pointed keratinous spicules at the tip and black keratin plugs in the center, accompanied by inflammatory reaction and fused into a patch. This disease is also associated with autosomal dominant inheritance and vitamin A deficiency. Children’s arm pimples have more causes, it is recommended to go to the hospital in time, the doctor to clarify the cause of the disease, symptomatic treatment, to reduce the adverse effects of the disease.