If someone was allergic to willow bark, what else would they be allergic to?

People who are allergic to willow bark are likely to be allergic to substances that are chemically related or derived from it. Willow bark contains salicin, which the body metabolizes to salicylic acid. Aspirin (acetylsalicylic acid) is a synthetic derivative of salicylic acid and is used for pain relief and anti-inflammatory purposes. Therefore, if someone is allergic to willow bark, they may also have a sensitivity to salicylic acid and, by extension, to aspirin because of their similar structures and pharmacological effects.

This connection makes the choice that includes aspirin and salicylic acid the most relevant option for those allergic to willow bark. Other choices involve substances that do not share the same chemical pathway or similar structural components as willow bark, making them less relevant in the context of potential cross-reactivity due to allergies.