Drugs, even aspirin, can make you ill. Take only the amount directed by your doctor or the drug manufacturer. Never give left-over prescription drugs to anyone else. Read medicine labels in good light to be sure you're taking the right amount and the right medicine. Cleaners can be dangerous, especially if they are not in their original containers and are mistaken for another product.
Wild mushrooms are often dangerous, since most varieties can be fatal if eaten.
If you notice strange stains, smells or behavior, or if cleaners or drugs are open near the victim, suspect poisoning. If you suspect poisoning, call your hospital emergency room immediately. If available, have the container with you. Some areas have poison centers you could call instead of the emergency room. Post appropriate emergency numbers by all the phones in the house.