Bumps on the arm need to take treatment according to the actual cause, such as eczema, keratosis pilaris, papular urticaria, etc. After diagnosis, choose general treatment, medicine or physical therapy. 1. Eczema: the cause of eczema is not yet clear, may be related to genetics, allergies, infections, etc., which can lead to the phenomenon of long arm bumps. For treatment, you can choose to use Dinaid cream and hydrocortisone butyrate cream externally, and at the same time, take oral antihistamines and other drugs to help improve its symptoms. 2. Keratosis pilaris: arm bumps may be keratosis pilaris, the cause of the disease is not known, there is a certain genetic predisposition, generally do not need special treatment, if there is a need for treatment or symptoms are serious, you can use topical retinoic acid cream or laser treatment. 3. Pemphigus urticaria: pemphigus urticaria can also cause arm pimples phenomenon, often caused by mosquito bites, the treatment can be used externally with glycerine lotion, oral antihistamine medication, etc., if necessary, can be prescribed topical glucocorticosteroids, such as hydrocortisone butyrate cream. There are many reasons for the arm pimples, after the symptoms suggest timely medical treatment, clear diagnosis under the guidance of a professional doctor to take standardized treatment, do not private treatment, so as not to lead to adverse consequences.