People who have spent a lot of time in contact with animals often develop animal-induced allergies, a significant percentage of which are quite serious  In a survey of current employees in major zoos, about 30 percent had animal-induced allergies
However, a zoo employee who develops a serious animal-induced allergy is very likely to switch to some other occupation
Among members of the general population who have spent as much time with animals as zoo employees typically have, the percentage with animal-induced allergies is significantly more than 30 percent.