Muscles, joints and bones
DMSO is generally given a expiry or retest date of 2 years from opening.
Pure DMSO has a freezing point of 18.5 degrees Celcius so in the winter and on cool days in the summer it tends to be solid. This is perfectly normal and one of the ways you can tell it is pure.
If you leave somewhere warm it will slowly melt and return to liquid. If you intend to dilute it with water it will remain liquid at temperatures above o degree Celcius. When it freezes in plastic, you may get some contraction of the bottle it is in. This is normal.