Wallpaper paste comes in three kinds:  flour, cellulose and vinyl.

Avoid the vinyl.  Some people are allergic to vinyl on their skin.

Flour will mold if it isn't sealed, or if it isn't perfectly dry before it is sealed.

Cellulose would be my choice.  It doesn't mold.  It is made from extremely refined and broken down plant fiber (usually wood).  It also dries clear, and is far less likely to reabsorb moisture, either from the atmosphere or from perspiration.  Somewhere on the container it should say 'cellulose' ('cellulose' in French, 'celulosa' in Spanish, 'zellulose' or 'zellstoff' in German).  The flour one should say something about 'wheat' on the label. 

I have a box of Metylan brand, made by Henkel (German), a very large worldwide company, and the labeling is very obvious.

Sue