Endotoxins are toxic substances found in the outer membrane of certain bacteria, particularly Gram-negative bacteria. They are composed of lipopolysaccharides and can trigger strong immune responses in humans and animals. When these bacteria die or are destroyed, endotoxins are released into the surrounding environment, potentially leading to inflammation and fever. The presence of endotoxins can be harmful, especially in medical settings. They are associated with conditions like sepsis, where the body's response to infection can become overwhelming. Understanding endotoxins is crucial for developing treatments and ensuring safety in pharmaceuticals and medical devices.