Magnesium sulphate (a.k.a. Epsom Salts, Sedlitz salt, and others) is a simple inorganic compound (MgSO₄ - 7H₂O) which has been used extensively - from at least the 1600s onwards - to treat a wide variety of medical conditions such as Asthmaplugin-autotooltip__plain plugin-autotooltip_bigAsthma

Asthma is a common, (and currently incurable) long term inflammatory disease of the airways of the lungs, characterized by variable and recurring symptoms such as reversible airflow obstruction, and bronchospasm. Episodes of asthma frequently feature wheezing, coughing, chest tightness, and shortness of breath., Pre-eclampsiaplugin-autotooltip__plain plugin-autotooltip_bigPre-eclampsia

"Pre-eclampsia is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease there may be red blood cell breakdown, a low blood platelet count, impaired liver function, kidney dysfunction, swelling, shortness of breath due to fluid in the lungs, or visual disturbances. Pre-eclampsia increases the risk of poor outco… and Psoriasisplugin-autotooltip__plain plugin-autotooltip_bigPsoriasis

"Psoriasis is a long-lasting autoimmune disease characterized by patches of abnormal skin. These skin patches are typically red, dry, itchy, and scaly. On people with darker skin the patches may be purple in colour. Psoriasis varies in severity from small, localized patches to complete body coverage.". It's currently on the WHO's list of essential medicines.

Its precise 'mechanism of action' however, is unknown - but excess magnesium appears to decrease the amount of the nurotransmitter acetylcholine released by motor nerve impulses, thereby slowing their response times.

Further info : Drugs.com