What can I give my 20 month old son for swollen gums and blisters in mouth?

Pain relief. Pain relief with Acetaminophen or Ibuprofen based on the child's weight should help. You could also try over the counter oral gel for pain relief - but use this sparingly and try to use gel without local anesthetic. Hope your feels better.
It depends. Though tooth eruption may cause swollwn gum, it does not cause blisters. Blisters on the gums suggest a viral infection, most common one may be human herpes simplex virus, but could be other viruses such as coxackie virus that causes "herpangina". The best thing for you to do would be to take your baby to a pediatrician.

Related Questions

I have tonsillitis at the moment, I have swollen gums and blisters on my lip, is this normal?

Not normal. See your dentist for a diagnosis and treatment of the swollen gums and blisters. It sounds like a herpes infection (herpetic gingivostomatitis), but you need to have a visual exam and supply a medical history to make an accurate diagnosis. See your medical doctor or an ENT specialist for the tonsillitis, which may or may not be related to the mouth infection. Read more...