What is the difference between erythema and hyperaemia?

Erythema is the physical sign of redness of an ectodermal structure like skin or the exocervix. It is caused by Hyperemia, which is the presence of increased blood flow to a particular structure.

Erythema is a physical sign, while Hyperemia is a physiologic process. Hyperemia can also occur in other parts of the body like in a myocardial infarct.