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Risks of Substances Found in Nature

Dr. Charlotte Means, D.V.M.
ASPCA National Animal Poison Control Center

We love our pets. When they’re ill or injured, we want to do what’s best for them. But what’s best? How do you weigh the risk of disease against the risk of treatment? In choosing treatment, is an herb or a tea better than an antibiotic or a diuretic? Every treatment option has some associated risk, and there is risk in doing nothing, too. As you and your veterinarian consider different ways to treat your pet, be aware of fallacies that may confuse the issues.




One such fallacy is that natural substances are not chemicals, that chemicals are synthetic substances and thus, that chemicals are “bad.” In reality, all of life is a series of chemical reactions. For example, water consists of two hydrogen atoms and one oxygen atom, combined through a chemical reaction. Digestion involves a series of chemical reactions. When we digest a potato, for instance, a complex carbohydrate is broken down to glucose, which all cells need in order to function.

Another fallacy is that the term “organic” means a substance has been produced without chemicals. In reality, the term “organic chemical” is simply a chemical with a carbon base. This includes synthetic insecticides – as well as potatoes!

Yet another common fallacy is that substances found in nature are “naturally” safe. In fact, many substances that could be classified as completely natural are among the most toxic substances there are. Botulism is a disease caused by ingesting the toxin produced by the bacterium Clostridium botulinum. It has been estimated that the dose needed to kill an adult human is less than one-millionth of an ounce. I once heard a radio talk show guest urge people to purchase strychnine for rodent control because it was “natural.” He was right; strychnine does come from a tree. However, a dog who ingests a lethal dose of strychnine, and does not receive timely veterinary care, will die from severe convulsions leading to suffocation within a few hours. Dead is dead.


Many products advertised as “all natural” also claim that no side effects can occur. In reality, the dose (quantity) determines the poison. If enough of a particular substance is ingested, toxicity will occur. For example, chocolate is toxic to dogs, but the dog must eat a sufficient amount based on his weight and the type of chocolate. Milk chocolate is not as toxic as semi-sweet chocolate, which is not as toxic as baking chocolate. An adult Great Dane can eat a much larger quantity of chocolate than an adult Chihuahua before a toxic quantity is reached. Some substances have a wide margin of safety – large quantities must be ingested, injected or absorbed before toxicity occurs. Other substances have a very narrow margin of safety. An example is the drug digitalis. There is a very narrow range between a therapeutic dose of digitalis and a toxic one. When this drug is prescribed, the owner not only needs to know how much and how often to administer it, but how to monitor the pet for signs of toxicity. Digitalis was originally isolated from foxglove (Digitalis purpurea), and an animal ingesting a certain amount of this plant would develop the same signs of toxicity as one who received an overdose of digitalis as a drug.

The route by which a substance is introduced into the body also makes a difference in the type and degree of harm the substance may cause. Several antibiotics must be given by injection to be effective. If taken by mouth, they would never leave the gut and could not fight the infection. Likewise, the species of animal influences toxicity. Non-steroidal anti-inflammatories, such as ibuprofen or naproxen, are much more toxic to dogs than to people on a comparative weight basis, as are some herbs, such as garlic. This is why though a little is good, a lot is not necessarily better, and why a person should never treat his pet with “people” medications.

The bottom line is that many factors must be considered in selecting the “best” treatment. For further information, see The Dose Makes the Poison: A Plain-Language Guide to Toxicology, 2nd ed. by M. Alice Ottoboni. And stay tuned to the next issue of Animal Watch for tips on assessing risk as you make health-care decisions for your pet.

Dr. Means, a veterinary toxicologist, is a member of the staff at the ASPCA National Animal Poison Control Center at the University of Illinois in Urbana.

© 2000 ASPCA
ASPCA Animal Watch – Spring 2000

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