Magnesium chloride (topical)

Tier 3 — weak evidence · Magnesium form · Topical · Muscle

Magnesium chloride hexahydrate applied as a 'magnesium oil' spray or bath flake — popular for local muscle cramp relief and as an adjunct when oral magnesium is poorly tolerated. Transdermal absorption is real but small and highly variable — insufficient to fully replace oral magnesium for systemic repletion, despite marketing claims. Best positioned as a local comfort tool and mild adjunct rather than a primary route. Skin stinging on broken skin is common. Oral remains the primary evidence-based route.

Dose: 10–20 sprays (200–400 mg) to limbs, or 1–2 cups flakes in bath