Promethazine hydrochloride is a histamine h1 receptor antagonist that counteracts capillary dilation caused by allergic reactions, reduces capillary permeability, and relieves wheezing symptoms caused by bronchial smooth muscle contraction. The drug is mainly used in the treatment of the following diseases: 1, skin mucous membrane allergy, including long-term, seasonal allergic rhinitis, vasoconstrictive rhinitis, allergic conjunctivitis, urticaria, food allergy, skin scratching signs. 2, motion sickness, including motion sickness, seasickness, airsickness. 3, nausea and vomiting, it should be noted that the adverse effects of the drug are sleepiness, drowsiness, manipulation of locomotives, high-altitude workers should be used with caution.