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During the spring and summer months of most countries in the northern hemisphere, many people suffer an allergic reaction to air-borne pollen and fungal spores that can disrupt their lives quite significantly. This condition is known as seasonal allergic rhinitis, but is more commonly called hay fever.

How common is hay fever?

In the UK hay fever affects about 20% of the population and often develops in childhood or during the teenage years. People with allergies and other conditions such as asthma are sometimes likely to suffer from hay fever too.

Some research has also shown that people become less sensitive to pollen as they get older, so it may disappear completely once a person reaches their mid forties.

The causes of hay fever

Hay fever is caused by an allergy to different types of air-borne pollen and, to a lesser extent, fungal spores.

Pollen is produced from a range of plants including trees, grasses and weeds. The pollen from these types of plants is tiny and carried by the wind, which is why they are easily breathed in.

Pollen that is carried by insects is too large to be carried by the wind and therefore rarely causes hay fever.

The hay fever season usually starts in mid spring with tree pollen such as birch and oak reaching a peak in the late spring. As the summer continues, grass pollens become more problematic and by the autumn, weed pollen and fungal spores are the main culprits.

Once breathed in, the pollen sets off an allergic reaction that causes the symptoms of hay fever that many of us know all too well. This allergic reaction involves the production of antibodies that attach themselves to special blood cells called mast cells, which produce the chemical histamine, as well causing the release of other chemicals from other types of cells. It is this histamine that causes the acute symptoms of hay fever, while the other chemicals can enhance and prolong the symptoms.

Symptoms of hay fever

The symptoms of hay fever vary from person to person, but most will experience the following:

• Itchy eyes, nose and throat
• Sneezing
• A stuffy nose (nasal congestion)
• A runny nose
• Watery eyes
• Red eyes

Less common symptoms may include wheezing (if the patient also has asthma), a loss of smell or taste and pain around the eyes and nose.

Many of these symptoms are due to inflammation caused by histamine and other chemicals, and are an attempt by the body to rid itself of the allergen; in this case the allergen is usually pollen.

Treatment of hay fever

Fortunately for hay fever sufferers, there is a wide range of effective medicines that treat the symptoms. These types of medicines are available from your doctor and some are available without a prescription from pharmacies.

These are often in the form of tablets, nasal sprays or eye drops and work by disrupting the allergic reaction to pollen in a way that reduces or prevents the symptoms.

Not surprisingly, many of these medicines are anti-histamines that block the actions of this chemical. Although these are very effective at reducing the symptoms of hay fever, some of them can cause drowsiness and the person taking the medicine must be careful if they plan to drive a car or operate machinery whilst taking them.

Other treatments include corticosteroids, which can reduce the production of many of the chemicals that are involved in the immune response, and medicines that reduce the production of histamine by mast cells.

The choice of medicine is often based on the most problematic symptoms. For example, a person with itchy eyes may choose eye drops whereas someone with nasal symptoms may be better using a nasal spray.

In extreme cases, a doctor may give a person a series of injections that reduces the immune reaction, with the aim of preventing symptoms. This type of treatment is called immunotherapy.

Prevention of hay fever

It’s difficult to prevent hay fever because the level of pollen in the air is extremely high at certain times of the year. Someone with severe hay fever may need to stay indoors or wear a mask to filter out the pollen. Other people could try the following precautions:

• Keep windows closed at home
• Use air-conditioning whilst in a car and if possible, fit a pollen filter
• Do not dry clothes outside
• Wash hands regularly to avoid transferring pollen to the eyes or nose
• Wear wrap-around sunglasses to keep pollen out of the eyes
• Avoid mowing grass and stay away from large areas of grassland
• Wash hands and hair after being outside
• Avoid other allergen such as animal fur, tobacco smoke and pollutants

Many countries publish a ‘pollen forecast’ which will allow sufferers to predict when they need to take medicine. Weather.com provides an allergy map.

If you are concerned about your hay fever, then you should discuss your symptoms with your doctor.