Ask Marilyn

Salt has been in salt deposits and the oceans for billions of years. So why do salt tablets have an expiration date?

—Reese Holser, Oakland, Calif. Many salt products, such as salt tablets, contain additives, and those additives can degrade over time. The salt itself (with the exception of certain types of sea salt) lasts indefinitely. In fact, salt has been extremely important as a preservative throughout history. It’s nontoxic, cheap and it even makes food taste better. Salt doesn’t lose its flavor over time, but as we all know from experience with saltshakers, it is affected by its environment. Humidity will make it clump. So alas, salt isn’t perfect!