For decades, scientists have puzzled over why people with allergies and asthma are overly sensitive to such irritants as cold, dry air and tobacco smoke. At least part of the answer may be that they harbor increased levels of nerve growth factor (NGF).
Researchers at Johns Hopkins University School of Medicine started to examine the role of NGF in allergic responses for several reasons. One was that NGF used to treat patients with Alzheimer disease caused excessive pain that involved an inflammatory response in lung and nerve cells similar to that of respiratory allergy. The researchers also found that people who were hyperresponsive to irritants had abnormally reactive nerves in their airways. And in animal studies, mice that were genetically engineered to produce excess NGF in their lungs developed hyperresponsiveness to irritants.
Voelker R. NGF Implicated in Allergy. JAMA. 2000;283(24):3189. doi:10.1001/jama.283.24.3189-JQU00004-4-1