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Hay fever

How common is hay fever?

Hay fever is common, and it's becoming more common.

Source:
Skoner DP.
Allergic rhinitis: definition, epidemiology, pathophysiology, detection, and diagnosis.
Journal of Allergy and Clinical Immunology. 2001; 108: 2-8.

Between 20 million and 40 million people in the United States have hay fever or another

allergy
If you have an allergy to something, your body overreacts when you're around it. The thing you are allergic to is called an allergen. Most allergens are harmless to most people. But if you're allergic to something, your body's system for fighting infection (your immune system) is too sensitive to that allergen. It triggers changes that we call allergic reactions. For example, pollen is an allergen for many people. If you're allergic to pollen, you'll sneeze and have runny eyes when pollen is in the air.

allergy with similar symptoms.

Source:
Nathan RA, Meltzer EO, Selner JC, et al.
Prevalence of allergic rhinitis in the United States.
The Journal of Allergy and Clinical Immunology. 1997; 99: S808-S814.

²

Source:
Conner SJ.
Evaluation and treatment of the patient with allergic rhinitis.
The Journal of Family Practice. 2002; 51: 883-890.

³
Overall, experts estimate that about 1 in 10 people get hay fever.

Source:
Skoner DP.
Allergic rhinitis: definition, epidemiology, pathophysiology, detection, and diagnosis.
Journal of Allergy and Clinical Immunology. 2001; 108: 2-8.

¹ And studies show that more and more are getting an allergy that gives them a stuffed-up nose or makes them sneeze.

Source:
Skoner DP.
Allergic rhinitis: definition, epidemiology, pathophysiology, detection, and diagnosis.
Journal of Allergy and Clinical Immunology. 2001; 108: 2-8.

¹
People of all ages and of both sexes have allergies such as hay fever, but more teenagers have allergies than any other age group.

Source:
Scadding GK, Drake-Lee A, Durham SR, et al.
Rhinitis management guidelines.
Martin Dunitz, London, UK; 2000.

⁴

And it's not just hay fever that's becoming more common. Other allergic conditions, such as

eczema
Eczema is a very itchy rash. It may be dark and bumpy and release fluid. Scratching makes it worse. You can get eczema anywhere on your body, but it is most common on the wrists, the insides of the elbows and the backs of the knees. If you have asthma or allergies you are more likely to get eczema than someone who doesn't have these conditions.

eczema and

asthma
Asthma is a long-term disease of the lungs. It makes you wheeze, cough and feel short of breath. Asthma attacks are caused by iflammation and narrowing of the airways, which makes it hard for air to pass in and out of the lungs.

asthma, are becoming more common, too. We're not certain why.

One idea is that the increase in allergic conditions is related to people having smaller families and better standards of cleanliness nowadays. This means children don't get as many

infection
You get an infection when viruses, bacteria, fungi or other tiny organisms get into your body. These bugs are so tiny that you can't see them without a microscope. For example, an infection in your airways causes the common cold. And an infection in your skin can cause rashes such as athlete's foot.

infections as they used to.

Source:
Fleming DM, Crombie DL.
Prevalence of asthma and hay fever in England and Wales.
BMJ Clinical Research Edition. 1987; 294: 279-283.

⁵

Source:
Durham SR (editor).
Summer hay fever.
ABC of allergies. BMJ Books, London, UK; 1998.

⁶

Some researchers think that getting lots of infections when you're young helps strengthen your

immune system
The immune system is made up of the parts of the body that are devoted to fighting infection. The body is constantly being threatened by infections from things like bacteria, viruses and parasites. The immune system fights these infections in different ways. At the microscopic level, the immune system uses antibodies and white blood cells, which travel in the blood and target infectious agents, such as bacteria. These microscopic parts of the immune system either kill the infectious agent directly, or take it to other parts of the body, like the spleen, where it can be dealt with. The lymph nodes are another important part of the immune system. Within them, white blood cells filter through the foreign material that has entered the blood, to see if there are any infections. When you have a swollen gland during a cold, this is actually a lymph node that is reacting to the infection. Unfortunately, it is possible for the immune system to become confused and to use its destructive powers to target healthy parts of the body. Diseases that result from this type of situation are called autoimmune diseases.

immune system. So, if children aren't getting so many infections, their immune systems may be affected. This could make them more likely to get allergies.

There's some evidence that first-born children, children from small families and children who don't go to nursery are more likely to get allergic conditions, such as hay fever.

Source:
Sheikh A, Strachan DP.
The hygiene theory: fact or fiction?
Current opinion in otolaryngology and head and neck surgery. 2004; 12: 232-236.

⁷ This might be because they get fewer infections in the first few years of their life than children from bigger families and children who mix with lots of other children at nursery. Some doctors may advise parents to make sure their young children mix with other children so that they get infections when they're young.

There's no evidence from research that having your child vaccinated increases their risk of allergic conditions.

Source:
Bremner SA, Carey IM, DeWilde S, et al.
Timing of routine immunisations and subsequent hay fever risk.
Archives of Disease in Childhood. 2005; 90: 567-573.

⁸

Sources for the information on this page:

Skoner DP.Allergic rhinitis: definition, epidemiology, pathophysiology, detection, and diagnosis.Journal of Allergy and Clinical Immunology. 2001; 108: 2-8.

Nathan RA, Meltzer EO, Selner JC, et al.Prevalence of allergic rhinitis in the United States.The Journal of Allergy and Clinical Immunology. 1997; 99: S808-S814.

Conner SJ.Evaluation and treatment of the patient with allergic rhinitis.The Journal of Family Practice. 2002; 51: 883-890.

Scadding GK, Drake-Lee A, Durham SR, et al.Rhinitis management guidelines.Martin Dunitz, London, UK; 2000.

Fleming DM, Crombie DL.Prevalence of asthma and hay fever in England and Wales.BMJ Clinical Research Edition. 1987; 294: 279-283.

Durham SR (editor).Summer hay fever.ABC of allergies. BMJ Books, London, UK; 1998.

Sheikh A, Strachan DP.The hygiene theory: fact or fiction?Current opinion in otolaryngology and head and neck surgery. 2004; 12: 232-236.

Bremner SA, Carey IM, DeWilde S, et al.Timing of routine immunisations and subsequent hay fever risk.Archives of Disease in Childhood. 2005; 90: 567-573.

This information was last updated on May 01, 2009

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© BMJ Publishing Group Limited 2009. All rights reserved.

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