Asthma is a chronic condition that can make breathing difficult. Many people with asthma have reactions to environmental factors including pollen, air pollution, and dust which can trigger asthma attacks. A recent study suggests scientists may be on track to find a new way to combat delayed asthma attacks known as “late phase” attacks.
During an asthma attack, breathing can become difficult as airways are clogged by excess mucus and inflammation of the tissue. A severe asthma attack can prevent air from moving in and out of the lungs and may require immediate medical treatment.
People who experience allergic reactions to pollen and other allergens may have an almost instantaneous response including mild to severe breathing difficulties. This kind of response is known as an “early phase” response because the reaction occurs very soon after exposure to allergens. Other symptoms may include wheezing, coughing, itchy eyes, and runny nose.
Late phase reactions can occur three or more hours after exposure to an allergen and often cause more severe breathing difficulties which may last up to 24 hours. People who find that their asthma symptoms become worse late in the day or at bedtime might be experiencing late phase reactions to allergens they encountered earlier in the day.
The mechanism triggering early phase asthma reactions has been understood by doctors for some time. However, late phase reactions have remained largely a mystery. Now, researchers at Imperial College London believe they have discovered why about half of all people with asthma experience late phase reactions several hours after they are exposed to allergens.
Using rats and mice as research subjects, scientists at Imperial College London traced the allergic reaction to sensory nerves in the airways. When allergens triggered the nerves, they activated reflexes that triggered other nerves to release the neurotransmitter acetylcholine. A neurotransmitter is a chemical that carries instructions from a nerve to other cells. In the case of acetylcholine, the instruction is for the airways to narrow, which makes breathing more difficult.
If this discovery in rodents also proves to be true in humans, it could lead to new research using drugs to counteract the nerve reflexes. Drugs that block the action of acetylcholine, known as anticholinergics, could prove to be beneficial for people who experience late phase reaction.
A previous clinical trial added the anticholinergic drug tiotropium for 210 patients who were also using steroid inhalers. The study showed that symptoms were improved when the anticholinergic drug was used, although the reason for the improvement was not clear. Tiotropium is currently used to treat chronic obstructive pulmonary disease (COPD).
The Imperial College London team is working to continue its studies to show a similar cause for late phase reactions in humans as in rats and mice. They are hopeful their study will provide a new direction for researchers to find a way to prevent late phase reactions for people with asthma.
Science Daily. Study Sheds light On Late Phase of Asthma Attacks. Web. August 31, 2011.
About.com: Asthma. Asthma & Your Immune System. Pat Bass. Web. August 31, 2011.
Asthma and Allergy Foundation of America. IGE’s Role in Allergic Asthma. Web. August 31, 2011.
Asthma and Allergy Foundation of America. Childhood Asthma. Web. August 31, 2011.
MedicineNet.com. Definition of Neurotransmitter. Web. August 31, 2011.
Reviewed September 1, 2011
by Michele Blacksberg R.N.
Edited by Malu Banuelos