The kids are heading off to school and Mike to work when Jan comes downstairs sneezing. Carol thinks Jan has flu and keeps her at home. The sneezing soon subsides and Jan seems perfectly well. Carol and Alice deduce it must have been an allergy and try to figure out what set it off. They first suspect the baking flour and garden flowers, but these are soon ruled out. Alice suggests that it may be an allergy to a person - perhaps the new half of Jan's family.
Mike comes home for lunch and goes up to see Jan. The moment he enters the room, she starts sneezing again and stops when he leaves. Carol and Alice begin to think that Jan is allergic to Mike. Then Jan has a very bad fit of sneezing when Tiger enters, and has no further reaction to Mike. They now deduce that Jan is allergic to Tiger. This means getting rid of Tiger. Mike knows the boys will be very upset. And they are. Saying goodbye is very difficult, especially when Tiger gets too distracted by the bone they gave him.
The girls, boys, Alice and Carol, and Mike in turn get the idea of bathing Tiger, not knowing everyone else has had the same idea. As a result, Tiger starts resisting when he gets a bath, much to the puzzlement of the person administering the bath. But next morning, Jan again reacts when Tiger approaches. So Mike takes Tiger to the grandparents. The family then realize Tiger's new flea powder got left behind, and Jan takes it. As she does, she starts sneezing again. They now realize it is the flea powder and not Tiger, and recall Mike and Tiger.
That night, the parents are relieved to see Tiger sleeping peacefully on Jan's bed.