A new study published in the Annals of Allergy, Asthma & Immunology says that two-thirds of all asthmatics also have an allergy. But many may not realize it.

Previously, it was known that children with asthma were more likely to have allergies, but it was thought this did not apply to asthma treatmentadults. However, the new study shows that a whopping 75% of asthmatics between ages 20 and 40 and 65% of asthmatics above age 55 have at least one allergy. If you think you may have an allergy on top of asthma, check with your doctor. They may need to be treated separately.

The study also said that the number of Americans diagnosed with asthma grows each year, as does the number of Americans with allergies. Currently, 26 million Americans have asthma and 50 million have allergies. It’s possible the growth of both asthma and allergies is linked, but hard to say for sure.

One explanation for the growth of each is the “hygiene hypothesis” which suggests that because our hygiene has improved, exposing us to fewer microbes, our vigilant immune systems have begun fighting off things they don’t really need to like dust and pollens. Another theory is that our improved knowledge of conditions like asthma is leading to more proper diagnoses, but not more actual cases. Hopefully the latter’s true.