Spring is here – and a quarter of those living in the UK start to cut their nose and itchy eyes.
April is a month to learn about pollen before grass pollen looking for hay fever in the summer.
But why in a few days is hay fever worse than others, regardless of high or low predictions of pollen?
Researchers led by a team from Bangor University believe they are a step closer to the answer.
Scientists have well predicted the overall level of pollen by warning those who have hay fever to take precautions, such as antihistamine tablets.
But Professor Simon Creer thought the picture was missing.
He has led the PollerGen project in Bangor, gathering researchers from as far as Australia, along with Met Office, Wales National Botanical Garden, Aberystwyth University Hall experts, and Worcester and Exeter University scientists.
"I myself am a hay fever patient and I know that in a few days, despite the high pollen forecast, I can be less affected than other days when the forecast seems to be lower," he said.
"It made me and others wonder whether the problem was the only high load of pollen, or whether the different grass pollen causes different levels of reaction."
However, there are big obstacles in determining which different herbaceous pollen can cause human hay fever.
There are hundreds of different herbaceous strains that produce different pollen, with varying amounts, and all seasons slightly different.
Mix the weather and different landscapes – and suddenly predict what kind of grass pollen becomes incredibly complex.
So PollerGen has used a different approach.
It has developed "environmental DNA" tests using the "metabarking" technique, and the first results were published in the science magazine "Nature Ecology & Evolution".
Throughout the allergy season, they have been able to identify fragments of material caught in an air, water or soil sample, and recognize grass strains using unique DNA "barcodes".
For the first time, it has allowed groups to start testing the link between some types of pollen and the days when most people with allergies are affected.
"The combination of different specialists has allowed us to find the initial answers," explained Dr. Georgina Brennan of Bangor, who decided to analyze environmental DNA data with Dr. Catrin Potter from Aberystwyth,
"Our task now is to develop a clearer idea of where pollen comes from, how it moves through the air and how different types of pollen can be linked to allergies."
However, researchers have not only focused on identifying different pollen strains – they have also been matched with data from medical operations and hospital admissions.
Health disorders and the distribution of some types of grass pollen can help improve the prediction of the Met Office and, in turn, help people improve their way of solving problems.
Research Charities The UK said recent findings showed more accurate pollen predictions for allergy sufferers "step closer".
"It is very welcome to help us better understand the species of grass pollen, especially if it can be used in the future to provide information to people affected by herb pollen allergy," said Amena Warner, Head of Clinical Services.
"We look forward to further results later this year and the benefits it will bring to those living with hay fever."