A new study led by researchers in the United States has shown that exposure to wildfire smoke might make some people more likely to fall ill by altering their immune systems.

According to the researchers who published the study in the journal ‘Nature Medicine,’ fire smoke appears to affect the immune system on a cellular level and people exposed to smoke showed an increase in memory immune cells that provide long-term immunity and biomarkers of increased inflammation and immune activity.

They also showed changes in dozens of genes related to allergies and asthma, researchers said.

“We’ve known that smoke exposure causes poor respiratory, cardiac, neurological and pregnancy outcomes, but we haven’t understood how,” senior researcher Dr. Kari Nadeau, chair of enviromental health at the Harvard TH Chan School of Public Health, said.

“Our study fills in this knowledge gap, so that clinicians and public health leaders are better equipped to respond to the growing threat of difficult-to-contain toxic wildfires,” she added.