Hi, Thanks for posting in HCM. I understand your concern. Defza contains Deflazacort, which is a glucocorticoid and is prescribed for anti-inflammatory conditions, and used as an immunosuppressant. Allegra contains fexofenadine, which is an antihistamine that reduces the effects of natural chemical histamine in the body and is used to treat the symptoms of seasonal allergies. Allegra and Defza interaction is not known, however might exist. Hence, kindly consult your Physician and get evaluated so that appropriate measures can be taken to overcome and prevent the same. Hope the information provided would be helpful. All the best.