Ingestion of household plants by children under age five is one of the leading reasons for inquiries to poison control centers nationwide. The best treatment for poisoning is to prevent it from ever happening. Teach children not to taste or play with or eat non-food plants both indoors and outdoors.
There are many houseplants which are perfectly safe to grow, but as lovely and harmless as others may appear, they can be toxic and/or dangerous in other ways. It is important to be as knowledgeable as possible about the plants growing in your home.
Chemicals concentrated in the cells of roots, leaves, bark and seeds serve as the plant's defense against insect and animal attack. Some of these compounds can be toxic, especially if ingested or touched by humans, and can result in adverse reactions.
A few plant families to be wary of include: the poinsettia family (Euphorbiaceae), the philodendron family (Araceae), the cactus family (Cactaceae) and the tomato family (Solanaceae). Dumb-cane (Dieffenbachia), in the Araceae family, has plant parts which contain oxalate crystals. If ingested these can cause the tongue to swell so severely that breathing stops. Crown of thorns (Euphorbia), a succulent in the Euphorbiaceae family, has toxic sap which can be quite irritating to the skin. Among the most poisonous are the compounds found in castor bean (Ricinus communis) and oleander (Nerium oleander), which can be deadly if ingested.
If a plant has been ingested, identify the plant, learn how much was eaten, contact the poison control center, watch for adverse symptoms, and bring the plant with you if you are advised to go to the nearest hospital emergency room. Always know the national poison control center contact number. (1-800-222-1222)
Learn which houseplants are poisonous and to what degree. The national poison control center can provide information on poisonous plants.
Be sure to properly identify and label houseplants with a tag on the branches rather than a stake that can be easily removed. It is important to note that plants often have several common names but only one botanical name. Contact the nearest botanical garden, cooperative extension service, retail nursery or florist for assistance in proper plant identification, or research horticultural books.
Exposure to poison is caused by ingestion of plant parts and/or by contact with the skin. Ingestion of plant parts can cause internal poisoning or heart or kidney failure. Skin contact can produce unpleasant symptoms such as dermatitis and allergic reaction. Brushing against sharp prickles, spines and thorns can also be extremely painful.
Do not grow potentially toxic houseplants within easy reach of a child. Understand which plants are safe to grow and display indoors.
Teach children not to taste or play with or eat non-food plants both indoors and outdoors.
Even though some plant parts will have a bitter, unpleasant taste, be prepared for emergencies with first aid supplies handy (a bottle of syrup of ipecac to induce vomiting). The poison control center will coach you on proper administering.
The North American guide to common poisonous plants and mushrooms by 
Handbook of Poisonous and Injurious Plants by 
