Molecules called “leukotrienes”—chemicals that get released from white blood cells when something irritates your airways or you inhale an allergen—were labeled the culprits. Medications have been developed to block the molecular cascade they initiate that leads to difficulty breathing.

But researchers from Case Western Reserve University think these molecules may not be the bad actors after all. Their research has been published in the Journal of Allergy and Clinical Immunology.

“We’ve found molecules that are alike in structure but generated through a completely different chemical pathway in the body,” said lead researcher Robert Salomon, the Charles Frederic Mabery Professor of Research in Chemistry.