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APRIL showers bring May flowers, or so the saying goes. But those beautiful spring blooms 鈥� and their plentiful pollen 鈥� mean sneezing, runny noses and itchy eyes for many people.

If this is you, and if you live in the UK, you can become a citizen sensor this spring by downloading the #BritainBreathing app and using it to record any allergy symptoms you develop. Doing so will help researchers learn more about when allergy symptoms are occurring at a population level and what the precise triggers are. Even if you don鈥檛 live in the UK, you can still download the app and use it for personal symptom tracking.

About , such as hay fever and asthma, and the incidence seems to be on the rise. The main culprit behind these ailments is pollen, with different types in the air at different times of year, but other factors such as the weather or levels of air pollution may also play a role.

The #BritainBreathing app matches anonymised symptom information with a rough geographical location, so that researchers can get an idea of where allergy symptom reports are clustered across the UK.

鈥淭hat might start to tell us a little bit more about what鈥檚 in the environment that鈥檚 causing the huge increase in allergies and asthma that we鈥檙e seeing 鈥� because it鈥檚 going up and up,鈥� says Sheena Cruickshank at the University of Manchester, UK, who is part of the #BritainBreathing team.

Thousands of people have joined the project so far and a .

Using data from the app and from other studies, Cruickshank and others are currently looking at how the interaction of pollens with pollutants in the air might be contributing to the rise in seasonal allergies.

Allergies occur when the immune system mistakes something harmless for something threatening, says Cruickshank. This happens when a substance triggers a signal of infection or damage in the body. 鈥淭hat鈥檚 what kind of gets your immune system going,鈥� she says.

鈥淚t鈥檚 very likely that some of the pollutants are providing both of those signals, alongside the pollen,鈥� says Cruickshank. Pollutants in the air may also be changing the structure of pollen in a way that makes it more stimulating to the immune system, she says.

It has been projected that climate change will increase the severity of the pollen season in Europe, and there are already signs its impact on plants has made the hay fever season in North America longer and more intense.

To find out more about the project and how to get involved, visit .

For other projects visit聽newscientist.com/maker.