How do I prevent my synthetic base layer from smelling?

Wash after every use if possible—this is the most effective approach. If you must wear it multiple days, rinse it out with water and hang it to dry overnight; this removes most bacteria and sweat residue. Soak in a 1:1 white vinegar and water solution for 30 minutes before washing to kill embedded bacteria. Look for silver-ion or polygiene-treated synthetics, which extend odor-free wear from hours to 1-2 days. Never store a damp synthetic base layer in your ski bag—that creates a bacteria incubator.