K.,
This definitely sounds like hand,foot, and mouth disease. It is a virus, like the other poster said. Look at his hands, and his feet and see if he has any blister like white spots there as well. There is also no medication for this. But I have to disagree with her about them not being able to get it again. I have known MANY children that get this virus about once a year (if not more). Be very careful with this though. Make sure that your baby is getting enough liquids, and is at least eating something each day. I have known children who refused to drink and had to be hospitalized for dehydration because of this virus. It is a miserable thing for them to have. I hope he feels better soon!!!!
Just to help you out, I have copied some info from the CDC website for you:
How It Is Spread
* Infection is spread from person to person by direct contact with infectious virus. Infectious virus is found in the nose and throat secretions, saliva, blister fluid, and stool of infected persons. The virus is most often spread by persons with unwashed, virus-contaminated hands and by contact with virus-contaminated surfaces.
* Infected persons are most contagious during the first week of the illness.
* The viruses that cause HFMD can remain in the body for weeks after a patient's symptoms have gone away. This means that the infected person can still pass the infection to other people even though he/she appears well. Also, some persons who are infected and excreting the virus, including most adults, may have no symptoms.
* HFMD is not transmitted to or from pets or other animals.
Illness
* The disease usually begins with a fever, poor appetite, malaise (feeling vaguely unwell), and often with a sore throat.
* One or 2 days after fever onset, painful sores usually develop in the mouth. They begin as small red spots that blister and then often become ulcers. The sores are usually located on the tongue, gums, and inside of the cheeks.
* A non-itchy skin rash develops over 1–2 days. The rash has flat or raised red spots, sometimes with blisters. The rash is usually located on the palms of the hands and soles of the feet; it may also appear on the buttocks and/or genitalia.
* A person with HFMD may have only the rash or only the mouth sores.
Also here is the link to the CDC website in case you want more information.
http://www.cdc.gov/ncidod/dvrd/revb/enterovirus/hfhf.htm#4
I hope your baby gets better soon!