[header] How to keep your glasses from fogging up [title] Purchase an anti-fog product to treat your glasses at home. [step] Many companies manufacture products specifically designed to prevent glasses from fogging. These are either a spray or gel, and when applied directly to your lens, will prevent fog by forming a barrier that protects against temperature change and moisture. 
[substeps] Most products require you to spray both sides of the lens, let dry, and wipe clean with a soft, dry cloth. Some products suggest longer dry times, while others require the spray or gel be rinsed off prior to wiping.