London: Delayed symptoms ravage half the people with asthma, several hours after exposure to allergens, says a new research.
Allergens -- pollen grains and dust mites -- can cause airways to tighten, triggering mild to severe breathing difficulties for asthmatics.
In the early asthmatic response, mast cells recognise these allergens, which release chemical signals that narrows the airways, the journal Thorax reports.
In research on mice and rats, an Imperial College London team linked the late response to allergens that trigger sensory nerves in the airways, according to an Imperial statement.
These nerves activate reflexes which trigger other nerves that release the neurotransmitter acetylcholine, causing the airways to narrow.
It means that drugs that block acetylcholine - called anticholinergics, which includes tiotropium - could be used to treat asthma patients who experience late phase responses.
A recent clinical trial involving 210 asthma patients found that tiotropium improved symptoms when added to a steroid inhaler, but the reason for this was unexplained.
"Our study in animals suggests that anticholinergic drugs might help to alleviate these symptoms, and this is supported by the recent clinical data," said Maria Belvisi, of Imperial College London, who led the research.