What is an allergy?

An allergy is an abnormal sensitivity or exaggerated reaction of the immune system to a substance, which, in the majority of people causes no symptoms at all. The substance that triggers the allergy is known as an allergen. Examples of allergens include plant pollen, pet dander, insect venom, dust, mold, foods and drugs. The body’s immune system makes an antibody which is also a protein, called IgE, in response to being exposed to an allergen. People with allergies, make IgE antibody that is specific for the allergen that they are allergic to, which then in turn can cause allergy symptoms. Common conditions associated with allergies are sneezing, itching, nasal congestion and drainage and are referred to as allergic rhinitis, or more commonly, hay fever. Eye itching and swelling are referred to as allergic conjunctivitis. Asthma, eczema and hives can also be conditions associated with allergies.

How do allergies develop?

Allergies have a strong genetic component. If you have allergies, others in your family are likely to have allergies as well. If one parent has allergies, a child has a 40% chance of having allergies. If both parents have allergies, there is a 7-8 in 10 chances that their offspring will have allergies. Even though children may be born with a predisposition to develop allergies, they do not always develop the same allergies as their parents.

Unlike eczema and food allergies which may start at a young age, inhalant allergies usually require several pollen seasons to develop. The signs and symptoms of inhalant allergies are usually not apparent until 3 years of age or older. However allergies can develop at any age with symptoms occurring later in life.

Children with allergies are also more likely to develop asthma. It is estimated that 80% of children with asthma have evidence of allergies. Therefore, recognizing and treating allergies can have a significant impact on reducing asthma symptoms.

How can I tell if I have allergies?

The symptoms most commonly associated with allergies include:

  • Runny nose (clear discharge)
  • Post nasal drip
  • Episodic sneezing
  • Nasal congestion (stuffy nose)
  • Coughing
  • Itchy/Watery eyes
  • Absence of fever
  • Wheezing (if asthmatic)

Less commonly noted symptoms include:

  • Headaches
  • Loss of sense of smell and taste
  • Ear itching, popping and fullness
  • Low productivity and poor concentration
  • Fatigue, irritability
  • Sleep disturbances
  • Snoring

How do you test for allergies?

Allergy tests, combined with the knowledge of your allergy specialist to interpret them, can give precise information as to what you are or are not allergic to. Testing done by an allergist is safe and effective for adults and children of all ages.

The most reliable and common test for allergies is a skin test. This simple, in office procedure introduces a very small amount of a specific allergen or allergens selected by the allergist based on your medical history. The allergen is introduced through an indention or “prick” on the surface of the skin. The results are available within minutes allowing your allergist to develop a treatment plan immediately.

Blood tests called RAST (radioallergeosorbent test) may be performed when skin testing cannot due to medications or skin conditions. Results are not available immediately as it generally takes a week or more to obtain results of RAST testing.

Which tests are better, skin or blood?

Allergy skin testing is the most accurate and preferred method of evaluating allergies. These tests are safe, minimally invasive, and easily interpreted. Blood assays or RAST may present the clinician with diagnostic challenges. Studies have shown variability between different labs so that results can be difficult to interpret. Blood tests also have decreased sensitivity compared to skin testing. Results from blood tests can often take a week or longer to be reported.
Credit: American College of Allergy, Asthma & Immunology