Promethazine is a medication that has many uses. Most often, it’s used for nausea and vomiting from cancer treatment (chemotherapy), surgery, and motion sickness. It can also be used to help people sleep before or after surgery, for allergies, and allergic skin reactions. Find out how promethazine treats hay fever and other allergy symptoms and how to take it. NHS medicines information on promethazine – what it's used for, side effects, dosage and who can take it. Promethazine is a sedating antihistamine used for allergic symptoms, motion sickness, and nausea. Due to CNS depression and anticholinergic effects, it is typically reserved for nighttime symptoms or specific indications where sedation is acceptable. Promethazine is used to relieve or prevent the symptoms of hay fever, allergic conjunctivitis (inflammation of the eye), and other types of allergy or allergic reactions. Promethazine is an antihistamine medication that prevents and treats the symptoms of an allergic reaction. It can also help you relax, go to sleep and relieve nausea, vomiting or pain before or after procedures. It works by blocking certain histamine receptors in your body, which helps to reduce itching, sneezing, and other allergy symptoms. It also affects parts of the brain that control nausea and. Promethazine, sold under the brand name Phenergan among others, is a first-generation antihistamine, sedative, and antiemetic used to treat allergies, nausea, and vomiting. Promethazine is used with other medications to treat anaphylaxis (sudden, severe allergic reactions) and the symptoms of the common cold such as sneezing, cough, and runny nose. Promethazine is also used to relax and sedate patients before and after surgery, during labor, and at other times. View promethazine hydrochloride information, including dose, uses, side-effects, renal impairment, pregnancy, breast feeding, contra-indications and important safety information. Promethazine is used to treat allergy symptoms such as itching, runny nose, sneezing, itchy or watery eyes, hives, and itchy skin rashes. It also prevents motion sickness, and treats nausea and vomiting or pain after surgery. It is also used as a sedative or sleep aid.