A longer grass pollen season means more Londoners could develop hay fever this year

. Credit: .

A longer grass pollen season will see more people develop hay fever according to one allergy expert.

Janette Bartle is an allergy nurse specialist and has been collecting samples of pollen for the last 11 years.

She uses a pollen trap which catches airbourne pollen on a sticky rotating drum. She then examines the findings under a microscope to track pollen levels.

Credit: PA

Hay fever is an allergic reaction to airbourne pollen. There are 2 million sufferers in London (that's one in 5 people).

Symptoms are most acute between May and Early August when plants are in bloom.> The most common allergy is to grass which affects 95% of hay fever sufferers.> Most treatments rely on steroid nasal sprays or antihistamines. Both treatments are most effective when taken before symptoms begin. Not drinking alcohol is also helpful as alcohol contains histamine.> The weather also plays a part. As a rough rule of thumb the hotter, drier and windier the weather, the more pollen is in the air.