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By Rabbi Dovid Cohen, Administrative Rabbinic Coordinator

Q. I know that there are special kosher rules for onions.  Can you give me some details on them?

A. Onions are a common example of a davar charif, a food that has a strong, pungent taste, which leads to it being treated in a stricter manner than other foods.  [Other common examples of a davar charif are garlic cloves, herring, horseradish, lemon and lemon juice, olives, pickles, radishes, scallions, vinegar, and whisky.]  That charif status affects how ta’am/taste transfers in several different ways.

Firstly, ta’am transfers into or out of a davar charif when it is cut, chopped, or ground, even if it is not hot.  This means that if you cut a pickle with a milchig knife, you cannot put that pickle into a corned beef sandwich.  [Since it is charif, the leniency of nat bar nat also does not apply.]  This halacha is only relevant for a solid davar charif, such as onion or lemon, since a liquid charif (like vinegar) cannot possibly be “cut”.  However, a second halacha of davar charif, known as mechalyah leh leshvach, applies to any davar charif, and for that we need a bit of background.

The general halacha is that if kosher food is cooked in a non-kosher (or meat, dairy, chametz, etc.) pot, that food becomes non-kosher.  If, however, the pot had not been used for 24 hours, the food is b’dieved permitted, since the absorbed ta’am is considered “stale”.  That final leniency does not apply if the kosher food was charif.  Rather, the kosher food reinvigorates (mechalyah leh leshvach) the stale non-kosher ta’am and renders the “kosher” food as non-kosher.  This is limited to cases where the kosher food was charif, and it makes no difference whether the original non-kosher was or was not charif.

There is debate regarding a third chumrah related to charif.  In most cases, if a liquid sits in a container for 24 consecutive hours, ta’am transfers between the liquid and the container, even if neither of them is hot.  There are some liquids (such as brine) which cause the transfer to happen in just a few minutes, and there is a machlokes whether davar charif should be included in this chumrah.  Shulchan Aruch says that it applies to charif as well, and, therefore, if whisky was in a non-kosher cup for a few minutes, the whisky would become non-kosher.  However, Shach argues that this special chumrah does not apply to davar charif, and it takes 24 hours for the transfer, just like with most other liquids.

These halachos (and a few lesser-known others) are only relevant while the food retains its charif characteristics.  Once, however, the charif is cooked or blended with other ingredients to the point that there is no longer a pungent taste, the charif status is gone, and it is treated like any other food.  For example, if a soup has some garlic in it, or if someone squeezes some lemon juice into their tea, the soup or tea are not charif, since their overall taste is not particularly strong; therefore, the strict status of davar charif will not apply to them.

This article first appeared in the Let’s Talk Kashrus column, Yated Ne’eman, February 14, 2025.