Allergies occur when your immune system reacts to certain foreign substances like dust, pollen, smoke that don’t cause a reaction in most people. 
Your immune system produces proteins known as antibodies that help protect you from unwanted invaders that could make you sick or cause infection. In the case of allergies, your immune system produces antibodies that identify a particular substance (allergen) as harmful, even though it isn’t. When you’re exposed to the allergen, the antibodies release a number of chemicals, such as histamine, that can inflame your skin, sinuses, airways, or digestive system.

Substances that most commonly trigger allergies include:

  • Airborne Allergens: This includes pollen, animal dander, dust mites, and mold.
  • Foods: Examples include peanuts, tree nuts, wheat, soy, fish, shellfish, eggs, and milk.
  • Medications: Examples include penicillin or penicillin-based antibiotics.
  • Insect stings: Bee stings or wasp stings can trigger allergies.

Risk Factors

  • A family history of allergies or asthma.
  • A child is more likely to develop an allergy than an adult.
  • Having asthma increases your risk of developing an allergy.

Allergic reactions may range from mild to severe. Severe allergies can trigger a life-threatening reaction called anaphylaxis.

Types of allergies
Symptoms are dependent on the type of allergy.

Hay fever. Also called allergic rhinitis, hay fever may cause:
•  Sneezing
•  Runny nose and nasal congestion
•  Watery or itchy eyes
•  Itchy nose, the roof of mouth or throat

Food allergy. Symptoms of a food allergy may include:
•  Tingling mouth
•  Swelling of the lips, tongue, face or throat
•  Hives
•  Anaphylaxis

Insect sting allergy. An insect sting may produce:
•  Swelling (edema) at the sting site
•  Itching or hives all over your body
•  Cough, chest tightness, wheezing or shortness of breath
•  Anaphylaxis

Drug allergy. Drug allergy signs and symptoms include:
•  Hives
•  Rash or itchy skin
•  Facial swelling
•  Wheezing
•  Anaphylaxis

Skin allergy. Your skin may:
•  Itch
•  Redden
•  Flake or peel


  • Skin test. Small amounts of material that can trigger allergies are pricked into your skin. If you’re allergic, you’ll likely develop a raised bump on your skin (hive) at the test location.
  • Blood test. It measures your immune system’s response to a specific allergen by measuring the amount of allergy-causing antibodies in your bloodstream
    1. Avoidance
      It’s important to identify and avoid your allergy triggers. This is a key step in preventing allergic reactions and reducing symptoms.

    2. Medications to reduce symptoms
      Over-the-counter and prescription drugs used to treat allergies.
    • Antihistamines. They treat sneezing, itching, and a runny nose. Newer oral antihistamines are less likely to make you drowsy.
    • Nasal corticosteroid sprays. They help prevent and treat nasal inflammation, nasal itching, and runny nose caused by hay fever.
    • Decongestants. They relieve congestion. Don’t use a decongestant nasal spray for more than two or three days at a time because it can actually worsen symptoms when used continuously.

    Simple steps taken at home can help relieve symptoms for certain allergies. Try these therapies.

    1. Nasal irrigation. This involves rinsing out your sinuses with a salt and water solution. You can use a neti pot or a specially designed squeeze bottle to flush out thickened mucus and irritants from your nose.
    2. Dust and dander elimination. If you’re allergic to dust or pet dander, you can reduce exposure to these allergens by frequently washing bedding and stuffed toys in hot water, maintaining low humidity, regularly cleaning.
    3. Moisture reduction. If you’re allergic to mold, you want to reduce moisture in damp areas, such as your bath, kitchen, and basement, by using a ventilation fan.

      Excerpt From: The Mayo Clinic. “Mayo Clinic A to Z Health Guide”.