What Causes an Allergic Reaction and How it is Diagnosed?

What are Allergies?

Allergies are your body’s reaction to a substance it views as a harmful “invader”. For example, coming into contact with what is normally a harmless substance, such as pollen, might cause your immune system (your body’s defence system) to react. Substances that cause these reactions are called allergens.

What Causes an Allergic Reaction?

Allergies appear to run in families and can be inherited. If you have a close family member who has allergies, you’re at greater risk for developing allergies.

An allergy starts when your immune system mistakes a normally harmless substance for a dangerous invader. The immune system then produces antibodies that remain on the alert for that particular allergen. When you’re exposed to the allergen again, these antibodies can release several immune system chemicals, such as histamine, that cause allergy symptoms.

Common allergy triggers include:

  • Pollen

Pollen is one of the most common causes of allergies. Pollen is a very fine powder produced by trees, flowers, grasses, and weeds to fertilize other plants of the same species. In people with pollen allergies, the immune system mistakenly identifies the harmless pollen as a dangerous intruder. It begins to produce chemicals to fight against pollen. The reaction leads to numerous irritating symptoms, such as sneezing, stuffy nose, watery eyes.

  • Dust Mites

Dust mites are microscopic arthropods that cause allergy and triggers asthma that lurks inside your own home. Symptoms are similar to those caused by a pollen allergy, but they often happen year-round instead of just during certain seasons.

  • Mould

Moulds are tiny fungi with spores that float in the air like pollen. They thrive in damp areas such as basements or bathrooms and piles of leaves or grass. A mould allergy can make you cough, make your eyes itch and cause other symptoms that make you miserable.

  • Animal Dander and Cockroaches

Dander are flecks of skin shed by cats, dogs and even birds. Dander can trigger allergies. You might also react to the proteins from oil glands in an animal’s skin or proteins from an animal’s saliva.

  • Insect Stings

Insects that cause allergic reactions include various bees, fire ants, yellow jackets, hornets, and wasps. If you get stung by an insect, you can expect pain, swelling, and redness and heat around the sting site. Those symptoms can last for a few days.

  • Latex

A latex allergy is an immune system reaction to proteins in natural rubber latex, a product made from rubber tree fluids. Symptoms range from minor skin irritation to life-threatening shock.

  • Certain Foods

When you have an allergic reaction to food, it usually happens within minutes after you eat the problem food. Peanuts, tree nuts, wheat, soy, fish, shellfish, eggs, and milk are among the most common foods that cause allergies.

  • Medications

Some people are allergic to certain medicines, such as penicillin or penicillin-based antibiotics. Symptoms can range from a mild reaction like a skin rash a few days after you start a drug to a severe and immediate reaction.

How is an Allergic Reaction Diagnosed?

Your doctor can diagnose allergic reactions. If you experience symptoms of an allergic reaction, your doctor will likely ask detailed questions about signs and symptoms, perform a physical exam, or keep a detailed diary of symptoms and possible triggers. Your doctor might also recommend tests to determine what’s causing your allergy. The most commonly ordered types of allergy tests are:

  • Skin Tests: A doctor or nurse will prick your skin and expose you to small amounts of the proteins found in potential allergens. If you’re allergic, you’ll likely develop a raised bump (hive) at the test location on your skin.
  • Challenge (elimination-type) Tests: Elimination diets are sometimes used to help pinpoint specific foods that might be causing symptoms of an allergic reaction. They can also help confirm the results of skin prick or blood tests.
  • Blood Tests: Your healthcare provider might do a blood test, especially if you use medications that could interfere with the results of a skin prick test. Specific IgE (sIgE) blood testing, commonly called radioallergosorbent test (RAST) or ImmunoCAP testing, measures the amount of allergy-causing antibodies in your bloodstream, known as immunoglobulin E (IgE) antibodies.

How can you prevent an allergic reaction?

Once you identify your allergy, you can:

  • Avoid exposure to the allergen.
  • Seek medical care if you’re exposed to the allergen.
  • Carry medications to treat anaphylaxis.

You may not be able to avoid an allergic reaction completely, but these steps can help you prevent future allergic reactions.

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