This may be applicable in some patients when a biopsy is needed and no blisters are available. The indirect immunofluorescence test shows that the serum of a patient contains specific antibodies that bind to different areas of the epithelium. Traditionally this biopsy is obtained from the buttocks. If no outbreaks are observed in this area, the biopsy is recommended for another area where the itching is observed. Dapsone changes the life span of red blood cells from an average of 120 days to 30 days.
Dapsone is known for possible hematologic changes as a common side effect.
The talk by Dr Joe Murray at the Celiac Disease Foundation meeting in June included a description of dermatitis herpetiformis, which I haven't seen discussed on this list. One was scratched blisters making a yellow crust on a red background, very colorful. The other was a batch of hives on a knee. He said the second, hives, type was more common in males. He said the cause of the dermatitis is pockets of gluten antibodies under the skin due to celiac disease.