Hi, welcome to the ehealth forum and I am glad to help you.
You seem concerned by the red itchy bumps on arms, back and chest.
Outbreaks of this sort are usually either viral or allergic.
Viral rash: While viral infections of the skin itself, like herpes or shingles (a cousin of chickenpox), are mostly localized to one part of the body, viral rashes are more often symmetrical and everywhere. Patients with such rashes may or may not have other viral symptoms like coughing, sneezing, or stomach upset (nausea). Viral rashes usually last a few days to a week and go way on their own. Treatment is directed at relief of itch, if there is any.
Allergic drug rash: Most allergic drug rashes start within two or three weeks of taking a new medication, especially if the person has taken the drug before. It is very unlikely for medicine that has been prescribed for months or years to cause an allergic reaction. Because there is usually no specific test to prove whether a rash is allergic, doctors may recommend stopping a suspected drug to see what happens. If the rash doesn't disappear within a week of not taking the medication, allergy is unlikely.
Although foods, soaps, and detergents are often blamed for widespread rashes, they are rarely the culprits.
Other rashes: Hives (urticaria) are itchy, red welts that come and go on various parts of the body. Most hives are not allergic, run their course, and disappear as mysteriously as they came. Heat rash is a skin irritation caused by excessive sweating during hot, humid weather. It can occur at any age but is most common in young children. Heat rash looks like a red cluster of pimples or small blisters. It is more likely to occur on the neck and upper chest, in the groin, under the breasts, and in elbow creases.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.
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