Scientists may have been wrong about what causes asthma, because it may not be the molecules blamed for decades. Researchers have identified "pseudo leukotrienes," which are compounds that trigger inflammation. These are formed by uncontrolled free radical reactions, not by normal enzymes. Pseudo leukotrienes have been found at much higher levels in people with asthma. Their amount exactly corresponded to the severity of the symptoms. The finding suggests a new way to treat asthma aimed at preventing the inflammatory spark rather than blocking its effects.