This chapter discusses the use of botulinum toxin in the head and neck, where proteins, botulinum toxin (BTX) are commonly used in otolaryngology. The anerobic, gram-positive bacillus, and clostridium botulinum produces BTX. Botulinum toxin interferes with the release of the neurotransmitter acetylcholine (ACh) from presynaptic nerve endings, resulting in temporary chemical denervation and muscular paralysis. ACh is the major neurotransmitter involved in skeletal muscle contraction. When injected intramuscularly at localized therapeutic doses, BTX produces partial chemical denervation of the muscle resulting in a localized reduction in muscle activity. The neurotoxin protein is the active component and the other proteins protect it from degradation. Higher amounts of protein antigen exposure are usually associated with a higher probability of antibody formation, where the amount of saline added determines the final concentration of the injected solution. Primary hyperhidrosis is a chronic idiopathic disorder that can affect the axilla, palms, feet, and face.