M.G.
If a kid has a rash on their hand, I would look to see if they have it around their mouth and feet too. If so, it could be hand mouth and foot disease. My daughter had it recently and I couldn't figure it out. I called my doctor and they told me about it. She didn't have it on her feet and mouth, just on her hands but my husband had it on his mouth and feet as well later on.
http://www.cdc.gov/hand-foot-mouth/about/index.html
Hand, foot, and mouth disease is a common viral illness that usually affects infants and children younger than 5 years old. However, it can sometimes occur in adults. Symptoms of hand, foot, and mouth disease include fever, blister-like sores in the mouth (herpangina), and a skin rash.
Hand, foot, and mouth disease is caused by viruses that belong to the Enterovirus genus (group). This group of viruses includes polioviruses, coxsackieviruses, echoviruses, and enteroviruses.