Derm Dx: Painful lip swelling, crusting and fissures

A 45-year-old male presents with a six-day history of swelling, crusting and fissuring of the lips. The patient reports significant pain, and says he has been unable to eat.

Prior to the eruption the patient reports he applied lip balm for chapped lips. He has no prior history of herpes labialis, and denies being in contact with individuals with similar eruptions. ...