Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a chemical compound, a salt with the formula MgSO4, consisting of magnesium cations Mg2+ (20.19% by mass) and sulfate anions SO2−4. It is a white crystalline solid, soluble in water but not in ethanol. Magnesium sulfate is usually encountered in the form of a hydrate MgSO4·nH2O, for various values of n between 1 and 11. The most common is the heptahydrate MgSO4·7H2O, known as Epsom salt, which is a household chemical with many traditional uses, including bath salts.The main use of magnesium sulfate is in agriculture, to correct soils deficient in magnesium (an essential plant nutrient because of the role of magnesium in chlorophyll and photosynthesis). The monohydrate is favored for this use; by the mid 1970s, its production was 2.3 million tons per year. The anhydrous form and several hydrates occur in nature as minerals, and the salt is a significant component of the water from some springs. Hydrates
Magnesium sulfate can crystallize as several hydrates, including:

Anhydrous, MgSO4; unstable in nature, hydrates to form epsomite. Monohydrate, MgSO4·H2O; kieserite, monoclinic. MgSO4·1.25H2O or 4MgSO4·5H2O. Dihydrate, MgSO4·2H2O; orthorhombic. MgSO4·2.5H2O or 2MgSO4·5H2O. Trihydrate, MgSO4·3H2O. Tetrahydrate, MgSO4·4H2O; starkeyite, monoclinic. Pentahydrate, MgSO4·5H2O; pentahydrite, triclinic. Hexahydrate, MgSO4·6H2O; hexahydrite, monoclinic. Heptahydrate, MgSO4·7H2O ("Epsom salt"); epsomite, orthorhombic. Enneahydrate, MgSO4·9H2O, monoclinic. Decahydrate, MgSO4·10H2O. Undecahydrate, MgSO4·11H2O; meridianiite, triclinic.As of 2017, the existence of the decahydrate apparently has not been confirmed.All the hydrates lose water upon heating. Above 320 °C, only the anhydrous form is stable.
Dracunculiasis, also called Guinea-worm disease, is a parasitic infection by the Guinea worm, Dracunculus medinensis. A person becomes infected by drinking water containing water fleas infected with guinea worm larvae. The worms penetrate the digestive tract and escape into the body. Around a year later, the adult worm migrates to an exit site – usually a lower limb – and induces an intensely painful blister on the skin. The blister eventually bursts to form an intensely painful open wound, from which the worm slowly crawls over several weeks. The wound remains painful throughout the worms emergence, disabling the infected person for the three to ten weeks it takes the worm to emerge. During this time, the open wound can become infected with bacteria, leading to death in around 1% of cases.There is no medication to treat dracunculiasis. Instead, the mainstay of treatment is the careful wrapping of the emerging worm around a small stick to encourage its exit. Each day, a few more centimeters of the worm emerge, and the stick is turned to maintain gentle tension. With too much tension, the worm can break and die in the wound, causing severe pain and swelling at the ulcer site. Dracunculiasis is a disease of extreme poverty, occurring in places with poor access to clean drinking water. Prevention efforts center on filtering drinking water to remove water fleas, as well as public education campaigns to discourage people from soaking their emerging worms in sources of drinking water.