Promethazine is a medication primarily used to treat allergies, motion sickness, and nausea. It belongs to a class of drugs known as antihistamines, which work by blocking the effects of histamine, a substance in the body that causes allergic symptoms. Promethazine can also be used as a sedative to help with sleep. This medication is available in various forms, including tablets, syrup, and injections. It is important to use Promethazine as directed by a healthcare provider, as it can cause side effects such as drowsiness, dizziness, and dry mouth. Always consult a doctor before starting or stopping the medication.