Leprosy reactions occur due to changes in the body's immune response against M. leprae bacteria and can develop at any time during or after treatment. There are two main types of reactions: Type 1 occurs in both tuberculoid and lepromatous leprosy and results from increased cell-mediated immunity that causes inflammation of existing and new skin lesions and nerves. Type 2, also called erythema nodosum leprosum, occurs in multibacillary leprosy patients with high bacterial loads and is caused by an Arthus-type allergic reaction to antigens from dead bacteria, resulting in tender nodules on the skin and potential inflammation of nerves, eyes, testes, joints,