Childrens Allergies

Patient: I have a 5 yr. old nephew that is currently staying with me. I cannot get hold of his parent(s). He has a history allergies to over 500 different species of trees, and he was also allergic to pet dander as a baby. He had not shown any recent signs of any allergic reactions to these until i picked him up from his mother today. He tells me he recently ate a cheerio’s cereal bar as a snack this afternoon, and lunch was a taco, and dinner was a cheeseburger with french fries. He says his tongue feels swollen, and his throat hurts when he swallows, and his voice sounds to him like it’s different. He also has a rash on his face on one side of his mouth, and his cheeks and ears are very red, but he doesn’t have a fever. I gave him a teaspoon of liquid benadryl about an hour ago, and I’m not sure it’s helped because it knocked him out. What are symptoms I should watch for in case I should go to the ER?