How can you tell the difference between razor burn and herpes?

Razor Burn & Herpes: Razor burns are initially caused by the act of hair being pushed back into the follicle during the process of shaving. As a result, the follicles become inflamed and the skin turns red - may develop an ingrown hair and/or larger bumps. Herpes, however, forms small painful blisters. They usually appear as small fluid-filled painful blisters on the skin and mucous membrane of the body.