Botulinum toxin is a neurotoxic protein produced by the bacterium Clostridium botulinum. It is one of the most poisonous substances known to exist. It can be dangerous if it is ingested or inhaled in large amounts. It can cause a serious illness called botulism, which can cause paralysis and even death. Botulinum toxin injections are used medically to treat various conditions involving muscle spasms or excessive muscle contractions. It is injected into the muscles to weaken or paralyze them, which can help to relieve muscle spasms, tremors, and other movement disorders