I know IBE said that Epi contains sulfur of some sort. You may want to consult your dermatologist about a possible long-term allergic reaction.
What symptoms are common in sulfa allergy?
Skin reactions. Skin reactions are the most common adverse reactions to sulfa medications, ranging from various benign rashes to life-threatening Stevens-Johnson syndrome and toxic epidermal necrolysis. Hives and
increased sensitivity to sunlight (photosensitivity) are also possible. There is a possibility that if the sulfa medication is continued despite a mild rash occurring, the rash could progress to a more severe form of skin reaction.
http://allergies.about.com/od/medicationallergies/a/sulfa.htm