My 5 yr old has herpangina, how long is it contagious for?

May be a week: It would be contagious while there are active lesions. The disease usually resolves in about a week. See this site for more information. http://www.ncbi.nlm.nih.gov/pubmedhealth/pmh0001964/.

Herpangina: Viral condition common in 3-10 year olds. A thorough examination and definitive diagnosis is important. Call your health care provider if: fever, sore throat, or mouth sores last for more than 5 days. Your child is having trouble drinking liquids or looks dehydrated, or fever becomes very high or does not go away. Good communication is very important.

Herpangina: As long as active lesions are present, usually within first week.