Causes of erythema multiforme include infection from the herpes simplex virus and medications such as penicillin. Erythema nodosum can be a result of pregnancy, ulcerative colitis or connective tissue disorders, according to the University of Maryland Medical Center. However, in half the cases of erythema, the cause is unknown.
Erythema is a skin condition that shows up as a rash and causes fatigue and lesions, explains the University of Maryland Medical Center. A person is most at risk of contracting erythema if he is between the ages of 20 and 30, has a family history of skin disorders and frequently exposes himself to the sun. Treatment options for erythema include drug therapies, nutrition, use of herbs and homeopathy.