As the only firstborn in my immediate family (though both my brother and I married firstborns in order to bring up the proportions), I would like to say that I knew all along that cats don't cause asthma, parents cause asthma:
"Among a group of very ordinary children born in a small town in the U.K. and followed from birth to the age of 5 to 6, levels of dust mite and cat allergens in the home were not related to their development of allergies or asthma," said lead author Dr. Paul Cullinan, a reader in respiratory epidemiology at the Imperial College School of Medicine's National Heart and Lung Institute in London.
"The most important factors were having a parent with asthma and being the first-born child in the family," he added.