Small blisters on the arm may be caused by eczema, or herpes zoster, and may be caused by white heat. 1. eczema: eczema is an inflammatory disease of the superficial dermis and epidermis caused by a variety of internal and external factors, the disease can lead to symptoms of small blisters on the arm, patients may also appear blisters at the vesicles oozing, with itching and other symptoms. 2. Herpes zoster: herpes zoster is due to latent in the body of varicella zoster virus reactivation of the disease, the disease can lead to patients with small blisters on the arm symptoms, patients can also appear blisters at the pain, burning sensation and other symptoms. 3. white prickly heat: white prickly heat is caused by sweat in the skin cuticle or cuticle below the sweat pipe overflow disease, the disease can also lead to patients with small blisters on the arm symptoms, blisters can be left after drying fine scales. In addition to the above diseases, other causes can also lead to the symptoms of small blisters on the arms, it is recommended to consult a doctor in time to identify the cause and ask the doctor to deal with it.