Ready for Review A poison is any substance that impairs health or causes death by its chemical action when it enters the body or comes in contact with the skin. Poisons are classified by how they enter the body. They can be ingested, inhaled, absorbed, and injected. Ingested poisoning occurs when the victim swallows a toxic substance. Alcohol is a depressant that affects a person’s judgment, vision, reaction time, and coordination. Drugs are classified according to their effects on the user: o Uppers (stimulants) o Downers (depressants) o Hallucinogens o Volatile chemicals Carbon monoxide is the leading cause of poisoning death in the United States each year. About 85% of the population is sensitive to poison ivy, poison oak, and poison sumac.