For your last pizza, thousands of single-celled organisms dedicated their lives. They died while assisting in the raising of the crust in the oven. Yeast is a common name for them.

Bakers sprinkle yeast on top of pizza dough dollops because yeast is a live, breathing fungus that works hard to give the saucy delight its characteristic fluff. Even though most individuals have no qualms about eating the organisms, a small percentage of the population is intolerant of them. People with yeast allergies who eat regular pizza with the leavening agent are at danger of suffering gastrointestinal problems, rashes, and, in the worst-case scenario, anaphylaxis.