Fexofenadine Allergia. Fexofenadine, sold under the brand name allegra among others, is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and. A recent study published in the journal of the american academy of dermatology (jaad) evaluated the efficacy of a combination consisting of antihistamines, topical. Allegra (Fexofenadine) 0,18…