What Is an Allergen?
An allergen is something that causes allergies. An allergic person's immune system mistakenly thinks the allergen is harmful, so it reacts and causes "allergy" symptoms. Someone who doesn't have allergies can be exposed to the exact same substance — like pet dander, for example — and not have any symptoms at all.
Allergens are often referred to as "triggers" for allergy and asthma, because they "set off" allergic reactions. There are different types of allergens, and a variety of allergic conditions that they can cause.
About Airborne Allergens
Many common allergens begin as "airborne allergens." They float through the air and can be breathed in, causing symptoms. These airborne allergens land on surfaces, too, and cause an allergic reaction when an allergic person comes in contact with them.
Common allergens are:
- Dust mite debris
- Mold allergens
- Pet dander
- Pollen particles/allergens
Sometimes these allergens are called "indoor/outdoor" allergies because they occur in your environment — say, when the pollen count is high during pollen season or when there are dust mites on indoor surfaces.
Back to TopHow Allergic Reactions Happen
The role of your immune system is to fight off harmful foreign substances — like viruses and bacteria. But sometimes it can "misinterpret" whether something is harmful or not. This is what happens with allergies.
If you are allergic to something and you breathe it in, swallow or touch it (depending on the type of allergy you have), you can get an allergic reaction.
- Your body produces antibodies to protect you from the allergen it thinks is harmful. The antibodies release chemicals to "fight off" the allergen.
- These chemicals — like histamines and leukotrienes — cause allergy symptoms such as sneezing or itching.
Exposure to common allergens can cause a variety of conditions with symptoms that range from mild to severe. Learn about Common Allergy Conditions.
Back to TopAllergy Facts and Figures
According to the Public Health Agency of Canada, 30% of Canadians suffer from allergies, while just over 8% of the population aged 12 years and older and 16% of children between the ages of 4 and 11 suffer from asthma. This adds up to billions of dollars in medications, physician services and missed days from school and work.
- The cost of asthma to the Canadian economy annually is estimated at between $688 million to $884 million in 2006 dollars. (The Allergy, Genes and Environment Network, Direct and Indirect Costs of Asthma in Canada, 1990)
- Health Canada estimates that non-food allergies are the most common chronic condition in Canadians 12 years of age and older.
- Asthma affects about three million people in Canada, six out of 10 of whom do not have control of their disease, according to the Asthma Society of Canada. It kills 500 people in Canada each year.
- The Allergy, Genes and Environment Network estimates that in the past two decades, the prevalence of food allergies has risen from less 1% of the population to as high as 5%.
- Genetics can affect your chances of having allergies.
- If one parent has allergies, you have a 1 in 3 chance of having an allergy.
- If both parents have allergies, you have a 7 in 10 chance of being allergic.
Index of Common Allergy Conditions
There are several different types of allergic conditions, each with its own set of symptoms. One or more of the common allergens -- including dust/dust mite allergens, pollen allergens, pet allergens, and mold/mildew allergens -- can cause these conditions
Allergic Asthma
Asthma is a chronic lung disease that is characterized by asthma attacks. During an asthma attack, or "flare," inflamed airways become narrowed -- making it harder to breathe. There are two types of asthma: allergic and non-allergic ("intrinsic"). According to CDC, asthma is a major public health problem in the United States.
Symptoms
Getting vaccinated is the best protection against contracting the flu.
- Coughing, which is sometimes uncontrollable
- Chest tightness
- Shortness of breath
- Wheezing
For more on asthma, visit the CDC's website at www.cdc.gov/asthma/faqs.htm.
To learn about non-allergic (intrinsic) asthma, check out the Asthma and Allergy Foundation of America's website at www.aafa.org/display.cfm?id=8&sub=17.
Back to TopEye Allergy (Allergic conjunctivitis)
This condition occurs when eyes are exposed to an allergen – usually pollen. With conjunctivitis, the membrane (whites) of the eye and the inside of the eyelid become irritated and inflamed. Eye allergy can happen alone or in conjunction with hay fever (seasonal rhinitis).
Symptoms
- Red eyes
- Itchy eyes
- Watery eyes
- Swollen eyes
Allergic Rhinitis
"Rhinitis" actually means inflammation of the nasal passages. This general term is used to describe the nasal congestion, sneezing and runny nose you can get due to allergies. Dust/dust mite allergens, pollen allergens, pet allergens, and mold allergens can cause rhinitis.
The allergic rhinitis caused by pollen is seasonal, and is often called "hay fever." But indoor allergens like dust mite allergens, pet allergens and mold allergens can cause rhinitis year-round. In addition, rhinitis is sometimes complicated by sinusitis, which is inflammation of the sinus cavities. Rhinitis can also trigger ear infections.
Symptoms
- Sneezing
- Stuffy or runny nose
- Itchy nose or eyes
- Itching on the roof of the mouth
Anaphylaxis
Food, medications, insect stings and exposure to latex can trigger anaphylaxis -- a serious allergic reaction that happens quickly. Airborne allergens do not cause anaphylaxis.
People with food allergies, in particular, may have severe and even life-threatening reactions if they eat a food they are allergic to. The most common food triggers are milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts
Symptoms
- A feeling of warmth/flushing
- Tingling in the mouth
- A red, itchy rash
- Light-headednes and/or shortness of breath
- Throat tightness
- Stomach pain/cramps and/or vomiting and diarrhea.
- In severe cases: drop in blood pressure that leads to unconsciousness and shock.
Anaphylaxis should be treated immediately with an injection of epinephrine (adrenalin). If you (or anyone you are with) begin to have an allergic reaction that could signal anaphylaxis, go to the closest emergency room immediately.
For more on this extremely serious allergic disease, visit the American Academy of Allergy, Asthma and Immunology: www.aaaai.org/patients/publicedmat/tips/whatisanaphylaxis.stm .
Back to TopDermatitis: Eczema (Atopic) and Contact
Atopic dermatitis is also called eczema. This common allergic condition is caused by allergen exposure to the skin. Eczema is an itchy rash that often occurs on the hands, arms, legs and neck, although it can cover the entire body. It can be triggered by airborne allergens like pet dander and dust mites. Contact dermatitis, on the other hand, is caused by direct contact with a substance that is causes a skin reaction (like latex or poison ivy), but not by common airborne allergens.
Symptoms
- Itchy, red and flaky skin
- Peeling of the skin
For more on this extremely serious allergic disease, visit the American Academy of Allergy, Asthma and Immunology: www.aaaai.org/patients/publicedmat/tips/allergicskinconditions.stm.
Back to TopHay Fever (Seasonal Rhinitis)
Seasonal allergic rhinitis is more commonly known as "hay fever." It's usually caused by an allergy to the pollen of plants, trees, or grasses. Depending on where you live and the pollen(s) you are allergic to, hay fever can happen in the spring, summer and/or fall -- and could last until the first frost. Seasonal allergies also can trigger allergic asthma.
Symptoms
- Sneezing
- Itchy and/or runny nose
- Itching and watery eyes
- Burning or itching on the roof of your mouth and/or your throat
Hives (Urticaria)
Urticaria, or "hives," can be caused by exposure to a allergen like food, medication or latex. Hives are not triggered by airborne allergens. Hives can be of any size and appear anywhere on the body. According to the American Academy of Allergy, Asthma and Immunology, approximately 25% of the U.S. population will have hives at least once in their lives.
Symptoms
- Itchy red bumps or swollen areas, often in clumps
For more on hives, visit www.aaaai.org/patients/allergic_conditions/urticaria.stm
Back to TopSinus Infection (Allergic Sinusitis)
This condition is caused by the swelling of the sinus cavities. The sinus cavities are the hollow spaces located behind the cheek bones, which is why your face can feel sore or tender to the touch if you have sinusitis.
A sinus infection can start as a cold but it is also often triggered by allergic rhinitis caused by allergens like pet dander.
Symptoms of Sinus Infection:
- Pain in the forehead, teeth or face
- Coughing
- Dark yellow or green nasal discharge
- Itchy eyes and sneezing
Read more about Colds and Flu.
Back to TopCold versus Allergies
Some allergic conditions, especially seasonal hay fever and allergic rhinitis, are easily confused with the common cold. That's because the symptoms are quite similar.
However, there are some general guidelines for determining "which is which," to allow you to take proper steps to relieve your condition and symptoms.
Allergies:
- Symptoms last up to several weeks
- Occurs in a "pattern," cropping up at the same time each year or after exposure to certain settings/situations
- Often includes "itchiness" in the nose or eyes
- Often include frequent sneezing and/or watery eyes
- Membranes inside nose may be swollen and pale or bluish in color
- Nasal discharge is clear and watery
Cold:
- Lasts for only a few days.
- Mucus is greenish/yellow.
- A fever is possible.
For more on cold symptoms and prevention, visit Colds and Flu.
Back to Top
