Hay fever and asthma sufferers are being encouraged to become "citizen scientists" to help experts understand what triggers an allergic reaction.

People who suffer from seasonal allergies are being encouraged to enter their symptoms into a free app called #BritainBreathing.

Experts will then be able to compare the data on symptoms to information on pollen counts, pollution levels and weather.

The information gathered could help lead to a better understanding of allergies and their triggers.

The app, created by experts from the Royal Society of Biology, the British Society for Immunology, and the University of Manchester, is free to download on Android.

"Seasonal allergies are increasing in the West but we don't know what is driving this," said Dr Sheena Cruickshank, from the University of Manchester and British Society for Immunology.

"It could be pollution, super pollens, increased cleanliness, or a combination of factors. What has been missing to answer this question is wide-scale human data about what is really happening. Because detailed information on pollen and pollution is available, we want to map Britain Breathing data onto that and perhaps come closer to understanding what really drives allergies, on both an individual and a national level."

Jon Kudlick, director of communications at the Royal Society of Biology, added: "This is a ground-breaking project as it will give users the chance to record and monitor the frequency of their own allergy symptoms, as well as then adding their experiences to the wider data set.

"Does air pollution add to the misery of those suffering with hay fever? Are people having more asthmatic symptoms in Manchester than in London, and if so why? These are the kind of questions we hope to help answer."