Allergies and the Immune System

Allergies are disorders of the immune system. Most allergic reactions are a result of an immune system that responds to a "false alarm." When a harmless substance such as dust, mold, or pollen is encountered by a person who is allergic to that substance, the immune system may react dramatically by producing antibodies that "attack" the allergen (a substance that produces allergic reactions). The result of an allergen entering a susceptible person's body may include wheezing, itching, runny nose, watery or itchy eyes, and other symptoms.

What is the immune system?


Illustration of the immune system
The Immune System - Click to Enlarge


  • Adenoids (two glands located at the back of the nasal passages)






  • Peyer's patches (lymphoid tissue in the small intestine)


  • Thymus (two lobes that join in front of the trachea behind the breast bone)

  • Tonsils (two oval masses in the back of the throat)

Disorders of the immune system


  • Cancer of the immune system


  • Immune complex diseases, such as viral hepatitis and malaria


How does a person become "allergic?"

Allergens can be inhaled, ingested, or enter through the skin. Common allergic reactions such as hay fever, certain types of asthma, and hives are linked to an antibody produced by the body called immunoglobulin E (IgE). Each IgE antibody can be very specific, reacting against certain pollens and other allergens. In other words, a person can be allergic to one type of pollen, but not another. When a susceptible person is exposed to an allergen, the body starts producing a large quantity of corresponding IgE antibodies. Subsequent exposure to the same allergen may result in an allergic reaction. Symptoms of an allergic reaction will vary depending on the type and amount of allergen encountered and the manner in which the body's immune system reacts to that allergen.

Allergies can affect anyone, regardless of age, gender, race, or socioeconomic status. Generally, allergies are more common in children. However, a first-time occurrence can happen at any age, or recur after many years of remission. Allergies tend to run in families. Hormones, stress, smoke, perfume, or environmental irritants may also play a role in the development or severity of allergies.

What is anaphylactic shock?

Anaphylactic shock, also called anaphylaxis, is a severe, life-threatening reaction to certain allergens. Body tissues may swell, including tissues in the throat. Anaphylactic shock is also characterized by a sudden drop in blood pressure. The following are the most common symptoms of anaphylactic shock. However, each individual may experience symptoms differently. Other symptoms may include:

  • Itching and hives over most of the body

  • Swelling of the throat and tongue

  • Difficulty breathing

  • Dizziness

  • Headache

  • Stomach cramps, nausea, or diarrhea

  • Shock

  • Loss of consciousness

Anaphylactic shock can be caused by an allergic reaction to a drug, food, serum, insect venom, allergen extract, or chemical. Some people who are aware of their allergic reactions or allergens carry an emergency anaphylaxis kit which contains epinephrine (a drug that stimulates the adrenal glands and increases the rate and force of the heartbeat).

Connect With MLH

Copyright 2014 Main Line Health

Printed from:
