Just about everyone has an allergy to something. Living here in Texas we have different types of mold as well as Mountain Cedar and wild grasses. It’s taken me years to develop some resistance to molds, but molds are not just outside. They are inside as well, every time you go back into the house you’re bringing the outside in. These molds are now in your carpet, furniture, bedding and clothing.
Some of the molds most favorite place is inside your a/c unit. Aspergillis molds love the cold wet environment of the evaporator coil in the a/c. This is one of the nastier molds that give people headaches and respiratory problems.
I had a friend with a little girl who suffered from asthma. After I told him his a/c was dirty he got the entire system. He also cleaned everything else in the house. 6 months later she was off her medication and acting like a normal kid.
Check your a/c every year and use the best paper pleated return air filters. It’s also good to spray a little Lysol on the coil twice a year. Ultra Violet lights also kill mold and bacteria.