When it comes to the side effects of Epsom salt, it's a good news / bad news story. The good news is that if you use Epsom salt externally -- say, to add to your bathtub or a foot soak -- you risk no known side effects. If you take Epsom salt internally -- if you use small amounts orally as an occasional laxative and follow the package instructions -- you shouldn't notice any side effects, aside from minor gastrointestinal, or GI, upset. But if you use it for any other purpose, or if you take a lot of it, there are many potential side effects, some of them serious.
What Is Epsom Salt and How Does It Work?
Epsom salt is a name for magnesium sulfate. Although this salt has many medical uses -- such as treating certain types of seizures, electrolyte imbalances or kidney problems -- the only approved do-it-yourself use for taking Epsom salt is to treat occasional constipation, following the package instructions exactly. The magnesium in the Epsom salt tends to draw fluid into the intestines, making the stool easier to pass. Other over-the-counter products work the same way. For example, the active ingredient in milk of magnesia, magnesium hydroxide, also draws fluid into the intestines.
Side Effects When Used as Directed
When Epsom salt is used in small doses for constipation, the side effects you are most likely to experience relate to the effect on your GI system. For example, your body might react by going a bit too far in the other direction, resulting in some diarrhea rather than constipation. You also might experience nausea. The dosages when used as a laxative are so small, relatively speaking, that side effects are not common.
Side Effects When Not Used as Directed
If you ingest magnesium sulfate for any condition other than constipation, it will not be in the form of Epsom salt, and it will be under careful medical supervision. If, however, someone were to ingest a lot of Epsom salt -- say, by accident -- or to use it not as directed, many more serious side effects could occur. According to the Drugs.com website, the side effects that can occur at higher doses and warrant immediate medical attention include "confusion; dizziness or lightheadedness; fast, slow, or irregular heartbeat; low blood pressure; muscle weakness; ... [and] sleepiness." Contact your doctor or poison control immediately if you experience these effects or suspect someone has taken a large dose of Epsom salt.
In the first half of the 20th century, using Epsom salt as an enema was a common practice, and people occasionally died from an overdose of magnesium. Unlike the skin, the mucous membranes of the colon can absorb the magnesium in Epsom salt, sometimes with tragic results. Likewise, using Epsom salt as a gargle has resulted in at least one magnesium-poisoning fatality in recent years. Even though Epsom salt is widely available over the counter, magnesium sulfate is not a substance to be trifled with; the Go Ask Alice website, which is run by Columbia University's Health Services, notes that it's wise not even to use it as a laxative without a doctor's supervision.
- Drugs.com: Epsom Salt Overview
- Drugs.com: Epsom Salt Side Effects
- Go Ask Alice: Are Epsom Salts a Safe Laxative?
- Journal of the American Medical Association: Magnesium Poisoning Following an Enema of Epsom Salt Solution
- Journal of Emergency Medicine: Hypermagnesemia-Induced Fatality Following Epsom Salt Gargles
- Photo Credit AndreyPopov/iStock/Getty Images
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