Health Vitamins & Nutrition Centre, Langley BC
Allergies by Christian Nordqvist
Allergies are hypersensitive immune responses to substances that either enter or come in contact with the body, such as pet dander, pollen or bee venom.

A substance that causes an allergic reaction is called an "allergen". Allergens can be found in food, drinks or the environment.

Most allergens are harmless, i.e. the majority of people are not affected by them.

If you are allergic to a substance, such as pollen, your immune system reacts to it as if it were a pathogen (a foreign harmful substance), and tries to destroy it.

Fast facts on allergies

Here are some key points about allergies. More detail and supporting information is in the main article.

Allergies are the result of an inappropriately large immune response
Some of the most common allergens are dust, pollen and nuts
Allergies have a range of symptoms that can include sneezing, peeling skin and vomiting
Anaphylaxis is a serious allergic reaction that can be life-threatening
There are a number of risk factors for allergies, including a family history
If you already have an allergy, you are more likely to develop an allergy to something else
In theory, any food has the potential to be an allergen
To diagnose an allergy, a clinician may take a blood sample.

What is an allergy?

Allergies are very common. Public health authorities estimate that about 20% of people in North America and Western Europe suffer from some degree of hay fever (allergic rhinitis, allergy to pollen).

A study published in JAMA Pediatrics (September 2013 issue) reported that children's food allergies cost both families and the government nearly $25 billion annually.

The number of people worldwide with allergies is increasing. According to Allergy UK, about 30-40% of people have an allergy at some stage in their lives. Some years ago, this increase was only apparent in industrialized nations. However, middle-income nations are now reporting higher rates of allergies across their populations.

The steepest increase in allergies has been observed in children, particularly food allergies.

A team of researchers from Northwestern University Feinberg School of Medicine reported in Pediatrics that about 8% of American children have some kind of food allergy. 38.7% of those with food allergies have a history of anaphylaxis (severe allergic reactions), and 30.4% are allergic to more than one food.

Researchers from St. Luke's Roosevelt Hospital Center, New York, found that foreign-born children who live in the USA have a lower risk of allergies. This risk grows the longer they remain in America.
Symptoms of allergies

When a person with an allergy comes into contact with an allergen, the allergic reaction is not immediate. The immune system gradually builds up sensitivity to the substance before overreacting to it.

The immune system needs time to recognize and remember the allergen. As it becomes sensitive to it, it starts making antibodies to attack it - this process is called sensitization.

Sensitization can take from a few days to several years. In many cases the sensitization process is not completed and the patient experiences some symptoms but never a full allergy.

When the immune system reacts to an allergen, there is inflammation and irritation. Signs and symptoms depend on the type of allergen. Allergic reactions may occur in the gut (digestive system), skin, sinuses, airways, eyes, and nasal passages.

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