How Can Vomiting And Diarrhea After Ingestion Be Treated?

This past Friday my son (13 yrs) had a Chicken McNugget meal from McDonalds, since then he s thrown up his other food for 2 days and had persistent diarrhea. As of Sunday he s been able to keep down food but the diarrhea persist. Are there any over the counter medications I can purchase that will help? Thank you