Dapsone, also known as 4,4'-sulfonyldianiline (SDA) or diaminodiphenyl sulfone (DDS),[3] is an antibiotic commonly used in combination with rifampicin and clofazimine for the treatment of leprosy.

[6] Other side effects include liver inflammation, methemoglobinemia,[7] and a number of types of skin rashes.

[10] Hypersensitivity reactions occur in 1.4% of persons treated with dapsone, and can be fatal in medical settings with low resources.

[29] The side-effect is more common and severe in those with glucose-6-phosphate dehydrogenase deficiency, leading to the dapsone-containing antimalarial combination Lapdap being withdrawn from clinical use.

[33] Abnormalities in white blood cell formation, including aplastic anemia, are rare, yet are the cause of the majority of deaths attributable to dapsone therapy.

When there is a "saturation gap" between a low ordinary pulse oximeter reading and a high arterial blood gas analysis result, methemoglobinemia may be suspected.

[10] Other adverse effects include nausea, headache, and rash (which are common), and insomnia, psychosis, and peripheral neuropathy.

[50] As part of the respiratory burst that neutrophils use to kill bacteria, myeloperoxidase converts hydrogen peroxide (H2O2) into hypochlorous acid (HOCl).

[56] Dapsone's anti-inflammatory and immunomodulatory effects[57] are thought to be its mechanism of action in treating dermatitis herpetiformis.

[citation needed] In the early 20th century, the German chemist Paul Ehrlich was developing theories of selective toxicity based largely on the ability of certain dyes to kill microbes.

Gerhard Domagk, who would later win a Nobel Prize for his efforts, made a major breakthrough in 1932 with the discovery of the antibacterial prontosil red (sulfonamidochrysoidine).

Further investigation into the involved chemicals opened the way to sulfa drug and sulfone therapy, first with the discovery of sulfanilamide, the active agent of prontosil, by Daniel Bovet and his team at Pasteur Institute (1935),[60] then with that of dapsone independently by Ernest Fourneau[61] in France and Gladwin Buttle[62] in the United Kingdom.

[31] Dapsone had been reported in a few cases to effectively treat acne, but the risk of hemolytic anemia kept it from being widely used for this purpose.

In the early 2000s QLT USA developed Aczone, a 5% dapsone gel that was shown to be effective against acne without causing clinically significant declines in hemoglobin levels, even in subjects with G6PD deficiency.

[65] 4,4-Diaminodiphenyl sulfone also finds uses as a curing agent for materials like epoxy resins and imine-based vitrimers, applications include in printed circuit boards, adhesives and coatings.