He is likely to be suffering from autoimmune blistering disorder. Most likely, it may be bullous pemphigoid (as there is blood eosinophilia, urticarial and tense bullous lesions on the skin). Skin biopsy for histopathology and direct immuno-fluorescence are required to confirm diagnosis. Treatment with steroids (Prednisolone, or DCP), tetracycline/nicotinamide combination, dapsone or additional immunosuppressives may be required. Consult a good dermatologist for proper management, as treatment may be required for years together.