What is the basic principle of toxicology?

The basic principle of toxicology states that “All things are poison and nothing is without poison; only the dose makes a thing not a poison.” This principle was postulated by Swiss physician and chemist Paracelsus about 500 years ago. 

What this implies is that the dose is what makes a substance toxic, where dose refers to the total amount of the substance absorbed during exposure. This is also known as ‘dose-response’. 

According to this basic principle of toxicology, any substance can be toxic and can cause harm when ingested or absorbed into the body in excessive quantities. The exact toxicity of a substance is influenced by a combination of factors including the dose of the substance a person is exposed to, the duration of exposure, and the route of exposure.