Sufferers face miserable summer as air pollution soars
Charity Allergy UK said hospital admissions have risen 500 per cent since 1990.
Reactions to foods, hay fever and cats are more frequent and intense, with 21 million sufferers in Britain.
From March to December last year alone, hospital admissions for allergies rose eight per cent on the same period in 2013.
There are more than 20,000 admissions a year of which 60 per cent - 12,560 - are emergencies.
Pollution The commonest allergies are hay fever, year-round rhinitis - often mistaken for a permanent cold - allergic asthma and eczema and food allergies.
Allergy UK's clinical director Maureen Jenkins said: "I think hay fever for Britain's 18 million sufferers will probably be bad this year. When you get good weather you also get more air pollution.
"The pollen attaches to the air pollution particles which means hay fever can be worse in towns than the countryside."
Hayfever for Britain's 18 million sufferers will probably be bad this year
One reason for the rise in allergies is thought to be that houses are now so clean that children do not build up resistance. Ms Jenkins said: "Nowadays about eight per cent of young children have food allergies whereas 40 years ago the figures were fairly insignificant.
"Allergic reactions are more frequent, often more severe and children can have reactions to more than one food."
A survey released by Hotpoint said one in five children suffers from allergies.
Allergy expert Dr Pixie McKenna said: "We often think of the great outdoors where the majority of potential triggers occur. "It's important to consider indoor allergens like dust mite, pet hair and pollen particles.
"Bacteria in childhood prime our immune system.
"Our environment has become so sterile we are missing out on exposure to both bad and good germs."
For some allergies are unpleasant and annoying but to others they can be deadly.
Nut allergy, for instance, can cause anaphylactic shock, bringing breathing and cardiac difficulties, unconsciousness and death. Allergy UK's deputy chief executive Lindsey McManus warned: "Anaphylaxis is a sudden reaction which can be terrifying at best and fatal at worst.
"There is a concerning lack of awareness of this fatal condition. Thousands of people are admitted to hospital every year and the number is soaring.
Hidden "Yet allergy is still a relatively 'hidden' epidemic. More must be done to raise awareness of the deadly condition if lives are to be saved."
Allergy UK said two in three Britons have no idea what to do if they see someone suffering an allergic attack. Patients need rapid adrenaline injections and immediate hospitalisation.
Meanwhile, Cats Protection said the number of pets being handed into its care because of allergies rose 10 per cent last year. It urged allergic cat owners to treat their condition with antihistamines, get rid of carpets and keep cats out of bedrooms but not to surrender their pets.