We have heard that the adhesive on that stamps in Israel is Kosher. We have also heard that some kids glues are classified as Kosher too - because kids might eat them. Readers have told us the same about U.S. stamps. Apparently they are veggie too! (Smithsonian National Postal Museum)
The United States Postal Service assures its customers that whey will not get fat licking stamps. There is no more than one-tenth of a calorie's worth of glue on every stamp. (Source: Absolute Trivia)
And then........................ Self adhesive stamps