Leprosy reactions involve a flare-up of inflammation in the body caused by complex immunological processes, linked to the remains of dead bacilli in the tissues. Reactions may occur before, during, or after treatment. They do not indicate a failure to control the leprosy infection. Normal antibiotic treatment is not affected, and completed treatment does not need to be restarted if a reaction occurs. Reactions occur in many people with leprosy, perhaps up to 50% of cases in some places, especially in patients with the multibacillary disease. Reactions may occur with obvious symptoms, such as red, swollen skin lesions, pain, muscle weakness, or sensory loss, but may also start insidiously, without any clear symptoms.
The factsheet is available in English, French, Spanish and Portuguese, and can be downloaded from the "Downloads" section below.