Why does DMSO crystallise, and what does that mean for storage?

Dimethyl sulfoxide (DMSO) is used as a solvent in research, industry and certain pharmaceutical applications. Pure DMSO can solidify at a cool room temperature. This is primarily a physical property, not evidence of poor quality. This article explains the phase change and safe storage principles, not how to prepare a mixture for self-medication.

What is DMSO?

DMSO is an organic sulfur compound and a powerful solvent. Highly pure DMSO is colourless and can be nearly odourless; smell is not a purity test. It can increase the absorption of other substances through the skin. Pharmaceutical uses concern defined products and do not authorise applying laboratory or technical products to the body.

Why does DMSO crystallise?

Pure DMSO has a melting point of about 18.5 °C. It can crystallise below that temperature; supercooling can delay the onset. Water content, purity and other dissolved substances alter phase behaviour. A crystallised product is therefore not automatically spoiled, and appearance or solidification alone cannot reliably determine its exact concentration.

Storage and handling crystallisation

1. Temperature control

Follow the specific product’s storage instructions. A blanket rule that every DMSO product must constantly stay above 19 °C is not useful: concentration, packaging and intended use can differ. Keep the container tightly closed and protected from contamination and incompatible chemicals.

2. No independent mixing

Dissolved substances can change the freezing point. This is not an invitation to mix DMSO with water, medicines, fragrances or technical chemicals. Heat generation, incompatibilities and increased skin absorption of other substances may matter. Defined laboratory formulations belong in professional procedures, not self-medication instructions.

3. Slow warming

For pure DMSO, the manufacturer describes slow reliquefaction at room temperature without detriment to the product. The specific product instructions remain decisive. Do not heat with an open flame, in a microwave or in an improvised hot-water bath. Speed alone does not establish chemical decomposition; avoid uncontrolled heat and contamination.

Applications and examples

In certain pharmaceutical formulations, DMSO can affect absorption through the skin . This does not mean that arbitrary active substances can be transported safely this way. Do not independently combine it with painkillers or other products; permitted use depends on the defined medicine.

In cryopreservation, DMSO is used at defined concentrations and in controlled procedures as a cryoprotectant. This concerns, among other things, water ice crystals and cellular damage, not keeping pure DMSO liquid as a general rule. Thawing, freezing and exposure conditions must suit the biological material.

Summary and safe interpretation

Crystallisation of pure DMSO near room temperature is a known physical property. For a specific product, the manufacturer’s instructions, purity and intended purpose matter. The manufacturer describes the melting point and reversible solidification; the ILO/WHO safety card lists skin absorption and chemical incompatibilities. This information does not recommend ingestion or skin treatment.

Tags:

DMSO, crystallisation, solvent, pharmaceuticals, melting point, cryopreservation, storage, skin absorption, product safety