Here's What You Can Substitute For Horseradish
With its unique and rather vicious blow-your-head-off flavor, you might assume that there's no such thing as a viable substitute for horseradish — but that is where you would be wrong. In fact, there are a number of options out there if you're looking to swap out something for horseradish.
One such possibility is mustard, which is in the same botanical family as horseradish — Brassicaceae (via Brittanica). Perhaps because they're actually plant relatives, mustard is just as pungent, although the flavor profile is slightly different (via LeafTV). However, the plus side is that the use of mustard as a horseradish substitute is extremely versatile. For example, if the recipe that you're using calls for freshly grated horseradish, you can use mustard seeds instead. Consider grinding them lightly in a mortar and pestle to bring out the flavor. On the other hand, if your recipe is looking for a horseradish sauce, you can use a creamy mustard, like dijon, for example.
Another option to substitute for horseradish
Another option to replace horseradish is the Japanese root wasabi, which is in the same Brassicaceae family. However, it will likely be significantly harder to find unless you are located in Japan or certain parts of Oregon (via The Wasabi Store). However, if you can get your hands on some wasabi root, you can use it exactly the same as you would horseradish.
In fact, wasabi is so close to horseradish that horseradish is often one of the leading ingredients in fake wasabi which comes with grocery store sushi and rolls served at low-end sushi joints (via Huffington Post). The other commonly used ingredient for fake wasabi? Mustard. Be careful with both of these substitutions, though. If you're removing horseradish from your recipe because someone you're cooking for is allergic, they will likely be allergic to mustard and horseradish as well, given the fact that they're all in the same family.