My 4 year old has very bright redness under his eyes and on his cheeks. he had his tdap and mmrv vaccines 7 days ago. are these related?

Probably not : If he was has having a reaction to the Tdap the time frame is off. It usually occurs 4hrs - 48 hrs post dose. For the MMRV vaccine that is a live virus vaccine. So if you're getting a reaction it would be because you're having a viremia 7-9 days post dose. There might be associated symptoms such as little vesicles around injection site, runny nose, fever,etc. if worried see his doc.