Necrosis can have various causes, which can lead to different types of damage to tissues: Hypoxia: Caused by ischemia (insufficient blood flow to an organ), shock, or respiratory failure Physical agents: External injuries like trauma, extreme temperatures (for example, frostbite), radiation exposure, or electric shock Chemical agents: Caused by poison, drug toxicities, or recreational drugs Biological agents: Bacteria, viruses, or fungi Immunologic reactions: Autoimmune responses (where the immune system attacks healthy tissues)