Vetnews | Maart 2026 16 « BACK TO CONTENTS Introduction to Poisoning Poisoning occurs when a toxic substance is swallowed, inhaled, or absorbed after coming in contact with the skin, eyes, or mucous membranes. Poisoning is also called toxicosis or intoxication. Because pets are unable to tell whether a substance is poisonous or not, they are often poisoned by eating something toxic, such as antifreeze or a poisonous plant. Pets can also be poisoned by a sting or bite from a venomous insect or snake, or even by a wellintentioned owner giving human drugs that are poisonous to animals. An animal can be poisoned after a single exposure (with effects most pronounced during the first 24 hours) or after repeated or prolonged exposure to a poison. All toxic effects depend on the dose—the amount of poison present—and on the species. A small dose may be undetectable and have no harmful effects, while a large dose can be fatal. Metabolism of Poisons Poisons can be absorbed via the digestive tract, skin, lungs, eyes, mucous membranes (such as those of the nose or eye), mammary glands, and uterus, as well as from sites of injection. Toxic effects may be local, or the poison can be absorbed and spread by way of the bloodstream. Some poisons are excreted by the kidneys. Others are excreted in the bile and collect in fat deposits. Still others are excreted in milk. In most cases, the body attempts to detoxify the poison. The liver does most of the metabolic processing that turns compounds into forms the body can use or excrete. This includes the detoxification of some substances. Unfortunately, when some poisons are metabolised, the new compounds created are more toxic than the original compound. Factors Affecting the Activity of Poisons The consequences of poisoning can depend on more factors than the toxicity of the poison itself. The dose (amount of the compound per unit of body weight) of poison is a primary concern, but the exact amount of poison an animal has been exposed to is seldom known. The number of times the animal is exposed and the length of time over which the exposure has occurred are important. The way in which the animal is exposed affects how much of the poison is absorbed, how it spreads through the body, and possibly how it is metabolised. The condition of the animal at the time of intake of the poison can also be a factor. For example, if the stomach is empty when an animal eats a poisonous substance, vomiting may occur. If the stomach is partly filled, the poison may be retained and lead to toxic effects. Environmental factors, such as temperature and humidity, affect rates of consumption and even whether or not some toxic agents are present. For example, many plant poisons are associated with seasonal or climatic changes, such as winter cold and rainfall. Different species of animals can react differently to a particular poison because of variations in absorption, metabolism, or elimination. For example, species unable to vomit, such as horses or rabbits, can be poisoned with a lower dose. The age, size, nutritional status, stress level, and overall health of an animal are important factors. In young animals, metabolism is compromised by underdeveloped systems. The chemical nature of a poison determines its ability to dissolve into different materials (water vs oil, for example). Poisons that dissolve in water spread through the body more easily than those that do not. Substances added to the active ingredient, such as binding agents, outer coatings, and sustained-release preparations, also influence absorption. Generally, as absorption is delayed, toxicity decreases. Droplet size is an important consideration in sprays and dips, because the dose increases when the droplets are larger. This is one of many reasons to closely follow label instructions and recommended applications. Only formulations intended for animals should be used. Diagnosis of Poisoning Diagnosis of poisoning is based on history, signs, tissue changes, and laboratory examinations. Giving your veterinarian a complete history is important to help him or her make an accurate diagnosis and begin appropriate treatment. You should have the following information available: 1) sex, age, weight, and number of exposed or sick animals; 2) a list of signs of illness in the order they appeared; 3) any prior disease conditions; 4) any medications the animal is receiving; 5) possible related events, for example, change in diet or water source, other medications, feed additives, or pesticide applications; 6) description of the environment, including access to garbage, machinery, or vehicles; and 7) recent past locations and when a geographic move happened (if applicable). By Steve M. Ensley, DVM, PhD, Department of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University Article
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