The latest health craze to hit social media: magnesium lotion.
Magnesium is an essential mineral that the body uses for a number of functions. It has long been thought to help with sleep when taken as an oral supplement, though there is little scientific evidence to back up that claim.
Influencers now promote magnesium in lotion form as an elixir for improving sleep as well as for addressing a wide range of problems, including cortisol and insulin imbalance, muscle soreness, fibromyalgia and arthritis.
"Did you know rubbing magnesium cream on your child's feet can help with sleep?" asks one woman on TikTok who goes by cottagecalderon and who promises that it can help with growing pains and improving mood.
"No midnight leg cramps," says a man on the account tap.the.orange.cart. "It works for me and my wife."
"Y'all," says another TikTokker, well over 40ish, "this magnesium lotion and spray is magic in the bottle."
The claim
Enthusiasts claim that magnesium lotion — specifically applied to feet — can improve sleep. Many also argue it can be applied all over the body to remedy a variety of other health ailments.
People are buying the idea, literally. One market research group estimated the market in 2024 for topical magnesium was more than $400 million.
The evidence
There is little proof that magnesium can be absorbed through the skin.
"The problem with this is that the skin is a barrier, not a sponge," says Nicholas Theodosakis, a dermatologist and researcher at Harvard University.
Most medications are best delivered orally, which allows for quick absorption into the bloodstream. A few kinds of substances are well suited to absorption through the skin, he says. Often, transdermal patches are used for medications that need to be slowly absorbed over time.
There's no evidence that magnesium is in this category.
Theodosakis theorizes that any benefits realized from magnesium lotion are likely from the massage used to apply it or the lotion's moisturizing ingredients.
" You apply a cream or a lotion or an ointment that contains some active ingredient and, yeah, your skin looks better than maybe some place you didn't apply it," says Theodosakis. "But that's because the cream itself promotes skin health. Anything that comes in like a cream base or an ointment base is just automatically gonna be good for the skin."
The nuance
Despite the lack of evidence, at least one doctor says if magnesium lotion is working for you — go for it. "I think the risks of applying magnesium to your skin are probably extremely small," says Dr. John Winkelman, a sleep expert at Harvard.
He says he had at least one patient report using "magnesium butter," for sleep. (" I thought you put that on toast, but no, in fact, you rub it on your legs," says Winkelman.) "She did say magnesium butter was helping."
Winkelman says in matters of sleep especially, placebo can be powerful — and he's not one to discourage whatever safe remedies work for his patients.
That said, Winkelman is not planning to recommend it anytime soon. Supplements and related products are not regulated by the Food and Drug Administration, which leaves consumers vulnerable to buying the lotion without knowing exactly what's in it.
For some of the sleep conditions that magnesium lotion supposedly treats, says Winkelman, there are medically proven treatments. Restless legs syndrome, for example — something some influencers say is eased with an application of magnesium lotion — has actual tested medical therapies.
"I really don't feel that it's fair to recommend things that I really don't think have been substantiated as effective," says Winkelman. "I'm a big believer in scientific evidence."
The bottom line
Though there is no proof that magnesium lotion promotes sleep or addresses medical problems, experts, including dermatologist Nicholas Theodosakis, agree that magnesium lotion likely won't hurt, except, he says, "in the pocketbook."
He notes that as a dermatologist, he sees many health fads. "I think it's just the nature of skin," he notes. "It's highly linked to emotional well-being and psychology and culture. Also, you just have quite a lot of it."
Copyright 2025 NPR