What is Allergy?

An allergy is an overly sensitive (hypersensitive) disorder of immune system. If you are allergic,

your immune system responds to your triggers in an abnormal way

These triggers are called allergen or antigen.  Antigens include pollen, dust mites, mold spores,

pet dander, food, insect stings, and medicines.


What are the types of allergen exposure?

Allergens enter your body by four different routes:

  1. Contact allergens enter your skin by touch. Example: poison ivy, latex gloves, jewelry.
  2. Ingestion. Example: food, drugs.
  3. Injection. Example: medications, bee sting.
  4. Inhalation. Example: pollens, dust mite, molds, animal dander.

What are symptoms of allergy?

Allergic Rhinitis

Allergic rhinitis (“hay fever”) is the most common of the allergic disease. Symptoms result from the inflammation of the mucus membranes of nose, sinuses, and throat. Hay fever symptoms include

  • Runny nose
  • Stuffy nose
  • Sneezing
  • Nasal itching (rubbing)
  • Itchy ears and throat
  • Post nasal drip (throat clearing)


Asthma is a breathing problem that results from the inflammation and spasm of the lung’s air passages (bronchial tubes). Common symptoms include:

  • Shortness of breath
  • Wheezing
  • Coughing
  • Chest tightness

Allergic Eyes

Allergic eyes (allergic conjunctivitis) is inflammation of the membranes that cover the surface of the eyeball and the inside of the eyelid. Symptoms of allergic eye include:

  • Redness under the lids and of the eye overall
  • Watery, itchy eyes
  • Swelling of the membranes

Allergic Eczema

Allergic eczema (atopic dermatitis) is an allergic rash due to inflammation of skin. Atopic eczema often occurs with hay fever and asthma. Symptoms include:

  • Itching, redness, and or dryness of the skin
  • Rash on the face, especially children
  • Rash around the eyes, in the elbow creases, and behind the knees, especially in older children and adults (rash can be on the trunk of the body)


Hives (urticaria) are skin reactions that appear as itchy swellings on your skin. Typical hive symptoms are:

  • Raised red welts (wheal and flare)
  • Intense itching

Anaphylaxis or allergic shock

Allergic shock (anaphylaxis or anaphylactic shock) is a life-threatening allergic reaction that can affect several organs at the same time. This response typically occurs when the allergen is eaten or injected. Common symptoms of anaphylaxis include:

  • Hives or reddish discoloration of the skin
  • Nasal congestion
  • Swelling of the throat
  • Stomach pain, nausea, vomiting
  • Shortness of breath, wheezing
  • Low blood pressure or shock

How is allergy diagnosed?

Allergy is diagnosed by history, physical examination, skin allergy test, allergy blood tests, and occasionally by deliberate allergen challenge. Allergy skin tests is the most common way to diagnose allergy.

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