 Other diagnoses in the differential diagnosis include bug bites and other blistering conditions such as bullous pemphigoid, linear IgA bullous dermatosis, and bullous systemic lupus erythematosus.The diagnosis may be confirmed by a simple blood test for IgA antibodies against tissue transglutaminase (which cross-react with epidermal transglutaminase), and by a skin biopsy in which the pattern of IgA deposits in the dermal papillae, revealed by direct immunofluorescence, distinguishes it from linear IgA bullous dermatosis and other forms of dermatitis.Additionally, the concomitant diagnosis of Celiac disease can be made without the need for a small-intenstinal biopsy if an individual has biopsy-confirmed dermatitis herpetiformis as well as supporting serologic studies (elevated levels of IgA tissue transglutaminase antibodies, IgA epidermal transglutaminase antibodies, or IgA endomysial antibodies).