An allergy is an adverse reaction that the body has to a particular food or substance in the environment.

Most substances that cause allergies are not harmful and have no effect on people who are not allergic.

Any substance that triggers an allergic reaction is called an allergen. Some of the most common allergens include:

• Grass and tree pollen (hay fever)
• Dust mites
• Animal dander (tiny flakes of skin or hair)
• Food allergen (particularly fruits, shellfish and nuts)

An allergy develops when the body’s immune system reacts to an allergen as though it is a threat, like an infection. It produces antibodies to fight off the allergen, in a reaction called the "immune response". The next time a person comes into contact with the allergen, the body "remembers" the previous exposure and produces more of the antibodies. This causes the release of chemicals in the body that lead to an allergic reaction.

Symptoms of an allergy can include

• Sneezing
• Wheezing
• Itchy eyes
• Skin rashes
• Swelling

The nature of the symptoms depends on the allergen. For example, you may experience problems with your airways if you breathe in pollen. Depending on your symptoms, the condition of your skin and any medication you are taking, you may be offered further tests to identify the allergen.

How common are allergies?

Allergies are very common. One in four people suffer from an allergy at some point in their lives. The numbers are increasing every year and up to half of those affected are children.

The reason for the rise is unclear. Some experts believe it is associated with pollution. Another theory is that allergies are caused by living in a cleaner, germ-free environment, which reduces the number of germs our immune system has to deal with. This causes it to overreact when it comes into contact with harmless substances.

Managing an allergy

In some cases, the most effective way of managing an allergy is to avoid all contact with the allergen causing the reaction. There are also several medications such as anti-histamines available to help control the common symptoms of many allergies.

Visit your local CarePlus Pharmacy for more advice.