Misdiagnosed As Arthropod Reaction? in Dermatitis Herpetiformis Posted November 12, 2015 · Report to Admin My biopsy showed arthropod bites/hypersensitivity to an external allergen/drug erruptions. Turned out, the rash was caused by a prescription drug I had been taking for years to sleep. Out of the blue. It recently started again when I started taking generic Ambien, which never caused problems in the past, but the lesions took two weeks to start popping up in many of the same places as before: abdomen, top and back of thighs, fingers, arms, hips.