More than 20 million people could suffer hay fever this summer as unusually high levels of pollen sweep across the UK.

Grass pollen, which is the worst culprit for causing symptoms and affects 95 per cent of sufferers, is set to reach its peak.

The Met Office warned that pollen levels have been unusually high in recent weeks and are set to be high on Sunday and Monday, with England worst hit, particularly London, the South East, the East of England, the East Midlands and the South West.

The NHS has joined the Met Office to work on research to help identify the grass pollen types that cause the most allergies, to help sufferers manage their condition.

Record numbers of people are suffering from hay fever, with allergic rhinitis the most common form of non-infectious rhinitis, affecting up to 30 per cent of adults and as many as 40 per cent of children.

Grass is the most common cause of hay fever in the UK and there are more than 150 species in the UK.

A survey of 2,000 hay fever sufferers by the Met Office revealed that 41 per cent suffer so badly that it ruins their whole summer.

But 57 per cent of sufferers did not know what type of pollen affects them, meaning they are not armed with the know-how to help combat their grass allergy.

Many are exacerbating their symptoms unnecessarily as 35 per cent said they frequently hang washing out to dry in the summer, unaware that pollen sticks to the clothes.

A further 40 per cent said they leave their windows open to cool their home in the summer, which lets pollen inside.

Yolanda Clewlow, manager of the UK pollen network at the Met Office, said: "We know how seriously hay fever can impact people's lives in the UK, particularly as a result of grass pollen.

"This has led to our involvement in a dedicated research programme to identify the most significant of the 150 different species of grass pollen in the UK.

"We aim to help inform hay fever and asthma sufferers and empower them in managing their symptoms more effectively.

"We urge anyone that suffers from hay fever and asthma to check our pollen forecast or to download our simple-to-use mobile app to receive notifications when pollen levels are at their highest."