Animals are usually asthma or allergy triggers.
The proteins found in animal dander, urine, feces, oil secretions and saliva, travels through the air on tiny particles lend in people nose, ears, eyes, and throat, triggering allergy and asthma symptoms directly or hours after the exposure.

Cats are one of the most potent asthma triggers (the worst offenders) and its urine is an especially strong trigger in many people.
Up to 50% of children with asthma have symptoms triggered by pets and if the pets are kept even though kids are asthmatic, the severity of their asthma symptoms will increase over time.