NEW YORK (Reuters Health) - A small, powerful molecule called nerve growth factor (NGF) may be responsible for making allergy sufferers more sensitive to irritants such as tobacco smoke, according to a report in the May issue of the American Journal of Re

NGF is better known to scientists for its role in helping to maintain nerve cells. It is being tested as a treatment for nerve and brain disorders. From these studies, ``researchers have discovered, to their surprise, that (NGF) may have a significant role in asthma, hay fever and other allergies,'' according to a statement from Johns Hopkins Medical Institutions. Dr. Alvin M. Sanico of Johns Hopkins Asthma and Allergy Center in Baltimore, Maryland, and his associates found that exposure to ragweed and grass pollen caused a significant increase in NGF levels in people who had reported chronic symptoms of allergic rhinitis, commonly known as hay fever. Inflammation and hyper-responsiveness to irritants are two features of hay fever that cause symptoms such as congestion. The cells in the allergic reaction produce NGF when inflammation is present. These cells are responsible for blending, storing and releasing NGF, which is then secreted in the upper airways and released in large quantities during an allergic reaction. Sanico and his colleagues tested whether an allergic reaction would increase NGF among 20 volunteers who had hay fever and 10 who had no history of chronic nasal symptoms. They provoked congestion, nasal irritation and sneezing by inserting ragweed or grass pollen sprays into nasal passages. Through nasal washings of the allergic group, the investigators found that baseline levels of NGF were much higher and that the presence of hay fever prepares nasal mucous for hyper-responsiveness. People who were hyper-responsive to irritants such as tobacco smoke had nerves in their airways that were unusually sensitive. Up to 36 million people in the US suffer from hay fever, and 14 million have asthma. Asthma, hay fever's counterpart in the lower airways, sent 1.9 million people to emergency rooms in 1995 alone. NGF is also present in the bronchial tubes of asthmatics, and they too experience inflammation and an increased responsiveness to irritants. But the researchers chose to study hay fever because the nose is more accessible for research than the lungs, Sanico told Reuters Health. He said the processes that take place in the nose more than likely occur in the lungs as well. Sanico noted that he hopes to see a drug that will block the effects of NGF molecules. ``Although there is still a distance between the findings and the treatment,'' he said, ``the study offers an explanation of why people who have allergies and asthma are more sensitive to irritants such as cigarette smoke, and how with this one molecule there is an increased responsiveness.''

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