Initially classified as antagonists of the histamine H1 receptor (H1R), they have been reclassified as inverse agonists, capable of stabilizing the inactive form of the H1R.20, 21, 22 Through this mechanism of action and also by antagonizing the effects of HA at the H1R, these drugs interfere with the allergic‐inflammatory processes, becoming the second‐generation antihistamines, medications of choice in patients with allergic rhinitis (AR), conjunctivitis allergic and urticaria. This evidence concerns the gene HRH1 and conjunctivitis.