The spray TikTok says loosens a stiff shoulder overnight

A 2017 review in Nutrients found magnesium barely crosses intact skin.

Magnesium spray clips are all over TikTok right now. Creators rub it into sore shoulders and say the ache fades by morning. I looked at the two clinical pilots and one major review behind the claim.

The product is magnesium chloride dissolved in water at roughly 31% concentration. Brands call it “magnesium oil,” but there is no oil in the bottle. The slippery feel comes from the dense salt solution against skin.

For the spray to relieve a stiff shoulder, magnesium ions would need to pass through the skin and reach the muscle or joint. Gröber et al. reviewed the transport science in a 2017 issue of Nutrients. The outermost skin layer, the stratum corneum, does not contain magnesium transporters. The only route in is through the small openings at sweat glands and hair follicles, and the reviewers found no evidence that a meaningful dose gets through intact skin.

Two small pilot studies have tested topical magnesium on patients. Engen et al. (2015) enrolled 40 women with fibromyalgia and had them apply four sprays per limb twice daily for four weeks. Some participants reported improved quality-of-life scores, but the study had no placebo spray group and was designed as a feasibility test, not a definitive trial. Kass et al. (2017) applied a magnesium cream daily for two weeks and measured blood magnesium. The change was not statistically significant.

Oral magnesium has a larger evidence base, and even that is thin for muscle cramps. A 2020 Cochrane review pooled 11 randomized trials with 735 participants and concluded that oral magnesium supplements are unlikely to provide a clinically meaningful reduction in cramp frequency in older adults.

One note on the sting. Many users feel a sharp tingle after applying the spray. Some brands market this as a sign of deficiency being “drawn out.” It is skin irritation from concentrated salt, not a diagnostic signal.

What do you reach for when a shoulder locks up?

Steve, the act of rubbing something into a sore shoulder for two minutes every night has value by itself. You warm the tissue, push blood through the muscle, and move the joint through a small range. Whether the magnesium adds anything beyond that is what the research cannot confirm yet. If it works for you and your skin tolerates it, keep going. I would add the shrug-and-drop and the doorway stretch so the spray is one piece of a bigger routine, not the whole plan.

Got an ache question? I read every one.

Keep moving,

The Ache Report

P.S. If the spray stings too much, apply it to damp skin right after a shower. The moisture dilutes the salt on contact and reduces the sting. Patch-test a small area on your inner forearm first and wait 24 hours before using it on a larger surface.

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