The concept of dose-response is central to toxicology. The dose of a toxin determines its physiological effects. At low doses, a substance might be harmless or even beneficial, but at higher doses, it can become toxic. This principle is encapsulated in the phrase "the dose makes the poison," attributed to Paracelsus, a key figure in toxicology. For example, while small amounts of selenium are vital for health, excessive intake can lead to toxicity.
