Poisoning can occur if a poisonous substance is swallowed (solids or liquids), breathed in (gases) or absorbed through the skin (normally liquids). Poisons are substances that damage the cells in the body. In order to cause harm they must enter or come into contact with the body. Many poisons are products we use every day and can be found in food, medications, household and garden substances. Accidental poisoning in dogs and cats is usually caused by substances we commonly have around the house, eg human medications and pest control products.