Last Week I Had A Chest X-ray. And The Pulmonary

Last week I had a chest x-ray. And the pulmonary Dr saw on the images small spots on my lung x-rays. Frontal and side profile. So now she's ordering a CT scan plus blood work. I'm puzzled with all these tests. What is she looking for? By the way I do have mild asthma and a cough I've had for a couple of years. We're thinking it's allergies.