Four-Leaf Clovers

In "The Allergy Problem" from "Peg + Cat," Peg discovers that she is allergic to four-leaf clovers and not Cat, as she thought at first. However, this shouldn't be biologically possible, as a regular clover would still have whatever allergen is present in the four-leaf clover that is triggering her sneezes.

Example of:
Abnormal Allergy