That's because pollen and other allergies can easily find their way indoors by way of clothing, open windows and air conditioners.
(That; 's; because pollen and other allergies can easily find their way indoors by way of clothing, open windows and air conditioners) (pollen and other allergies; can easily find; their way indoors)
That pollen and other allergies
's can easily find
because pollen and other allergies can easily find their way indoors by way of clothing, open windows and air conditioners
their way indoors