Science
Mechanism of Action
The efficacy of strontium in mitigating skin irritation, stinging, burning, tingling, and itching is attributed to the strontium cation. This cation is believed to interact with epidermal nerve cells, thereby preventing or counteracting irritation sensations, potentially by altering nerve cell depolarization/repolarization or interfering with nerve impulse transmission. Strontium also possesses anti-inflammatory, anti-pruritic, and analgesic qualities. Its observed antimicrobial activity in non-skin applications is linked to its strong basicity, creating a high pH environment unfavorable for bacterial growth.
Research
Clinical Evidence
Medium confidence2%
Key findings
- 01 Topical formulations containing strontium cation, particularly within a 1.3% to 2.6% range (150-300 mM) calculated as strontium, have demonstrated effectiveness in suppressing various skin irritations, including those induced by alpha-hydroxy acids, alpha-keto acids, and capsaicin. A 4% strontium chloride gel (delivering approximately 1.3% strontium cation) significantly reduced the intensity and duration of cowhage-induced itch in healthy subjects, outperforming hydrocortisone and diphenhydramine.
- 02 An open-label study involving 50 participants showed strontium cream reduced pruritus symptoms in patients with Hidradenitis Suppurativa.
- 03 In vitro studies (non-skin application) indicated that 10 mM and 100 mM Strontium Hydroxide exhibit potent antibacterial effects against peri-implantitis-associated bacteria, attributed to its high pH.
Transparency
Dusting Analysis
Strontium Hydroxide's cosmetic application is strictly limited to pH regulation in depilatory products, not as a primary active ingredient for its strontium cation benefits. Its use at any concentration requires careful adherence to regulatory maximums and pH limits due to its corrosive nature, precluding typical 'dusting' scenarios.
The Formula
Formulation
Stability
Strontium Hydroxide is hygroscopic and sensitive to air, readily absorbing carbon dioxide to form strontium carbonate. It requires storage in tightly closed containers and handling under an inert atmosphere, such as nitrogen, to maintain stability.
Conflicts
- acids
- carbon dioxide (CO2)
Safety
Safety Profile
Strontium Hydroxide is classified as a severe skin, eye, and respiratory irritant, and is corrosive, capable of causing severe burns and eye damage. In the EU, its use in cosmetic products is restricted to pH regulation in depilatory products at a maximum concentration of 3.5% (calculated as strontium), with the final product pH not exceeding 12.7. Under these specific conditions, the SCCS has deemed its use safe. However, a proposed CMR (Carcinogenic, Mutagenic, Reprotoxic) 1B reprotox classification for strontium salts, including Strontium Hydroxide, is ongoing, raising significant safety concerns.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Despite the anti-irritant potential of the strontium cation, Strontium Hydroxide's severe corrosive nature, stringent regulatory restrictions to highly specific product types (depilatories), and a pending CMR 1B reprotox classification make it an ingredient to generally avoid in precision skincare formulations.
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References
Sources