# Reusable and safe endothermic reaction [closed]

I am looking for a reusable endothermic reaction that is safe to both touch and handle, it needs to be able to be stored in a jacket and light enough to do physical activity. Any suggestions?

There are many endothermic physical processes such as melting ice or sublimation of solid carbon dioxide $\ce{CO2}$. One should also mention thermoelectric cooling effect (Peltier device), which is is rarely effective in practice, yet still an option.
A suitable endothermic chemical reaction would probably be an electrolytic dissociation of certain salts, among which dissolving ammonium nitrate $\ce{NH4NO3}$ in water is probably one of the most well-known and effective examples.