Red vesicular spots on the chest and arms need to be treated with medication according to the cause, and common causes include herpes zoster and contact dermatitis. 1. Herpes zoster: Herpes zoster is caused by varicella zoster virus infection, can occur in any part of the body, such as the chest, abdomen and limbs, manifested as pimples and blisters on the surface of the skin, with redness around the periphery, accompanied by pain. Oral antiviral drugs, such as acyclovir tablets, vasiclovir tablets, etc.; oral analgesic drugs, such as acetaminophen tablets, gabapentin capsules, etc., and topical antiviral creams, such as acyclovir cream, penciclovir cream and so on. 2. Contact dermatitis: If the skin on the chest and arm area comes into contact with external substances, such as animal fur, flowers, etc., contact dermatitis may be triggered, which manifests itself as erythema, edema, pimples, blisters or even blisters on the surface of the skin, and may be accompanied by itchiness, burning, distension, and pain, etc. The skin can be treated with topical glucocorticoid. Local topical glucocorticoid ointment, such as mometasone furoate cream, halometasone cream, etc., while oral antihistamine drugs, such as loratadine tablets. All of the above drugs should be used under the guidance of a professional doctor, avoid self-medication. Red vesicular spots on the chest and arms may have other causes, it is recommended to go to the hospital in time to improve the examination, to clarify the cause of the disease to give targeted treatment.