Endotoxins are degradation products from dying gram-negative bacteria and complex aggregates of acidic lipopolysaccharides (LPS). They are composed of a lipophilic lipids part and hydrophilic polysaccharides. In humans, endotoxins can cause immune responses like fever (pyrogenic threshold is approx. 0.1 ng/kg bodyweight). Unlike bacteria themselves, endotoxins are extremely heat and pH-stable and therefore withstand sterilization.