Epsom salt baths and magnesium sprays: can skin absorb magnesium?

What are Epsom salts, flakes and magnesium oil?

• Epsom salts are magnesium sulphate crystals, about 10% magnesium by weight. They are sold for baths and, separately, as a laxative.
• Magnesium flakes are usually magnesium chloride, also for baths and foot soaks.
• Magnesium oil and sprays are concentrated solutions of magnesium chloride. They feel oily but contain no oil.

They are marketed as a way to top up magnesium “through the skin”, bypassing the gut, for sleep, cramps and recovery.

Can magnesium get through skin?

Very little, if any. The outer layer of skin is designed to keep water-soluble, electrically charged substances out, and magnesium in solution is exactly that. In 2017 a group of German researchers reviewed the evidence and concluded that the case for transdermal magnesium is scientifically unsupported. The studies that claimed an effect were small, mostly without a control group, and often unpublished or funded by sellers.

In other words, the magnesium in a bath mostly goes down the plughole.

Why do people feel better after a magnesium bath?

Warm water relaxes muscles, a bath before bed can help you wind down, and expecting to feel better helps too. Those are real benefits, but they don’t depend on magnesium. If you enjoy a salt bath, there is no harm in it for most people.

Are Epsom salts or magnesium sprays risky?

Externally, mainly skin irritation: magnesium oil commonly stings or itches, especially on broken skin or after shaving. Don’t use bath salts if you have open wounds or a skin condition without advice.

By mouth, magnesium sulphate is a strong laxative. Take it only as a product labelled for that use, at the stated dose. Too much can cause severe diarrhoea and, rarely, dangerously high blood magnesium. See constipation.

What should you do instead?

If cramps are the reason you’re trying a spray, read magnesium for leg cramps first: oral magnesium doesn’t beat placebo for ordinary night cramps either.

If you want more magnesium, eat more magnesium-rich foods or take a well-absorbed oral form such as citrate or glycinate. Our comparison of forms covers the rest.