Scientists have stumbled on a potential new treatment for delayed asthma attacks which can occur several hours after exposure to allergens, a study shows. A team from Imperial College London found that blocking sensory nerve functions stopped a \"late asthmatic response\" in mice and rats, according to the (BBC). Around half of people with asthma experience delayed symptoms. The charity Asthma UK says the research could help the understanding of asthma. Writing in the journal Thorax, researchers say the late asthmatic response happens because the allergen triggers sensory nerves in the airways. These nerves then set off a chain reaction which causes the release of neurotransmitter acetylcholine, which causes the airways to narrow. If these findings translate to humans, it will mean that drugs called anticholinergics - which block acetylcholine - could be used to treat asthma patients who suffer from delayed attacks. These attacks can often happen at night, three to eight hours after the sufferer comes into contact with grass pollen or house-dust mites, for example. A typical early asthmatic response occurs within an hour of exposure to allergens. At present, steroids are the main treatments for asthma but they are not effective for all patients. The data produced by the study suggests that anti-cholinergic therapy may be effective in patients that observe a late phase response to allergen. Separate recent clinical studies also showed that an anti-cholinergic improved symptoms and lung function in asthma patients.