Asthma symptoms are commonly triggered by allergens in the environment, such as pollen and dust mites. These stimuli can cause the airways to tighten within minutes, causing breathing difficulties which range from mild to severe.
Many sufferers also experience a “late asthmatic response” three to eight hours after exposure to allergens, causing breathing difficulties which can last up to 24 hours. New research, led by scientists from Imperial College London and funded by the Medical Research Council, looked at why around half of people with asthma experience a “late phase” of symptoms several hours after exposure to allergens. In research on mice and rats, the Imperial team have found evidence that the late asthmatic response happens because the allergen triggers sensory nerves in the airways. These nerves activate reflexes which trigger other nerves that release the neurotransmitter acetylcholine, which causes the airways to narrow. If the findings translate to humans, it would mean that drugs that block acetylcholine – called anticholinergics – could be used to treat asthma patients that experience late phase responses following exposure to allergens
