According to John Collard, clinical director of Allergy UK, antihistamines reduce most people's hay fever symptoms, including sneezing or itchy, watery eyes.
“Older-style sedating antihistamines, such as Piriton, are taken three to four times a day and can make you drowsy,” says Collard. "Non-sedating antihistamines, such as loratadine, are only taken once a day and do not cause drowsiness. Different brands work better for different people."
How do antihistamines work?
Antihistamines work by blocking the action of histamine, a chemical released by the body after it has been exposed to pollen.
Pierre Dugué, consultant allergist at Guy's Hospital in London, says that histamine is kept in certain cells in the body known as mast cells. In an allergic reaction, these cells let the histamine leak into the blood and tissue, causing inflammation.
Antihistamines are chemical structures that block the action of histamine at special sites (receptors) in the skin, nose, blood vessels and airways.
Are antihistamines safe?
Older types of antihistamines, such as Piriton, are effective but can make you feel sleepy. So, they could be dangerous if you're driving a car or working with machinery.
“More modern drugs containing loratadine do not usually cause drowsiness," says Collard. "There have been some side effects in some patients, such as dry mouth. As long as you're aware of this, you should be fine.”
How to take antihistamines
Collard says antihistamines generally have a good safety record. “That’s why they’re available over the counter. People with symptoms should take them regularly, not just on odd days when they feel bad. They work better if you take them right through the hay fever season.”
Antihistamines come in nasal sprays and eye drops if you don't want to take tablets. These target specific parts of the body so are useful if you only get itchy eyes, for example. For children, some antihistamines are available as a liquid.
It's sometimes helpful to start antihistamines a couple of weeks before your symptoms start, if they start at a predictable time.
Read more about treatments for hay fever.
