Allergies-All you wanted to know about

Allergies-All you wanted to know about

Allergies are hypersensitive response of the body’s immune system to the allergens.

What causes allergies?

The immune system attacks harmful foreign substances or organisms entering our body by producing IgE antibodies. Normally the immune system does not produce antibodies in response to the substances we get exposed on an everyday basis. But in an allergic reaction, these substances trigger an immunological reaction by releasing antibodies, which causes the immune system to remember it as a harmful substance. When there is another exposure to the same substance, the body releases chemicals that cause allergic reactions (1).

Allergens are the substances which create an allergic response in the body. Allergy can develop at any age, or any substance, even to a previously exposed well-tolerated substance.

Common allergens are pollen, peanuts, milk, soy, shellfish, wheat, tree nuts, metals, latex, penicillin, insect stings, dust, and some drugs (1).


The symptoms depend upon the allergen and the individual’s immune system. The symptoms and severity of symptoms can differ from one person to another. Certain diseases/disorders are caused by allergic reactions. They are angioedema, allergic conjunctivitis, allergic asthma, allergic rhinitis, and anaphylaxis. The symptoms differ based on the type of allergy.

Types of allergies:

  1. Food allergy an allergic reaction to certain food substances. The most common food items causing allergy are milk, soy, eggs, peanuts, pine nuts, tree nuts, shellfish, and wheat (2). The symptoms include vomiting, abdominal pain, loose stools, cough, trouble swallowing, wheezing, dizziness, and shock.
  2. Drug allergy: some people are allergic to certain drugs/medications. Penicillin is one of the drugs to cause an allergic reaction. The symptoms of drug allergy are skin rashes, itching, difficulty in breathing, and sometimes anaphylaxis (1).
  3. Skin allergy: skin allergy, sometimes considered as contact dermatitis or eczema. It can be caused by contact with latex, metals, and poison oak. Symptoms of skin allergy are raised, red, irritated, swollen rashes, itching, and/or pain (3).
  4. Allergic rhinitis: allergic rhinitis is the allergic response to inhaled substances such as pollen, some perfumes, pet hair, dander, dust, and weeds. The symptoms are itching in the nose, redness of the nose, watery discharge from the nose, sneezing, and sometimes blocked nose (4).
  5. Insect sting allergy: some insect stings can cause an allergic reaction. They are honeybees, wasp, red ants, hornets, mosquitoes, and some bugs. The symptoms of insect allergy are pain, redness, itching, swelling, rashes and sometimes serious anaphylactic reactions characterized by low blood pressure, dizziness, and shock (5).
  6. Dust allergy: allergic reaction just after sweeping or cleaning the house can be due to dust allergy. The symptoms of drug allergy are itching of the skin, sneezing, cough, runny nose, cough, shortness of breath, and itching of the eyes (2).
  7. Eye allergy: eye allergy is also known as allergic conjunctivitis. It can be caused by dust, pollen, animal hair, irritants, perfumes, and dust mite. The symptoms of eye allergy are itching of the eyes, swollen eyelids, watery discharge, redness, and irritation (6).
  8. Allergic sinusitis: it is the allergy of the sinuses. The symptoms of allergic sinusitis are nasal block, fever, headache, nasal discharge, postnasal drip, the heaviness of head, and cough (3).
  9. Latex allergy: latex allergy can cause serious allergic reactions in sensitive individuals. The symptoms of latex allergy are itching, rashes, running nose, wheezing, cough, shortness of breath, and sometimes shock (2).
  10. Other types: other types of allergies include cockroach allergy, mold allergy, and pet allergy.


Diagnosis of allergy is done by clinical examination findings and diagnostic tests. The tests performed to confirm the diagnosis are:

  1. Skin prick test: In this test, the skin is pricked with a minute amount of suspected allergen and observed for allergic reactions (7).
  2. Patch test: Small patches containing allergens are placed on the back of the body and examined for allergic reactions (6).
  3. Blood test: The blood levels of IgE antibodies are measured in this test.


The treatment method depends on the type of allergy and symptoms. The treatment modalities are:


  1. Antihistaminics: they act against histamine responsible for inducing allergic reactions and decrease the symptoms of allergy such as itching, redness, and runny nose (5).

Example: diphenhydramine, cetirizine, and fexofenadine.

  • Adrenaline: used to increase heart rate in severe allergic reactions such as anaphylaxis and shock.
  • Corticosteroids: corticosteroids decrease the inflammation and swelling of the allergic reactions. They are used in allergy, asthma, and anaphylaxis.
  • Mast cell stabilizers: they stop the release of chemicals from mast cells causing allergic reactions (8).

Example: omalizumab, ketotifen

  • Antileukotriene agents: they are used in the long term treatment of allergies.

Example: montelukast, zafirlukast

Avoidance of allergens:

After allergy testing and confirming the allergens responsible for causing allergic reactions, it is noble to avoid those allergens which will help in preventing allergic reactions (8).


This therapy involves injecting purified allergens in very small quantities and desensitizing the immune system to the allergens (2).


1. davidson, sir stanley. immunological factor sin disease. davidson’s principles and pracrtice of medicine. s.l. : elsevier, 2010.

2. ALLERGIES. american academy of allergy asthma and immunology. [Online] [Cited: july 19, 2019.]

3. Allergies. mayoclinic. [Online] [Cited: july 19, 2019.]

4. Alana Biggers, MD, MPH. Everything You Need to Know About Allergies. healthline. [Online] june 8, 2018. [Cited: july 19, 2019.]

5. Allergy. wikipedia. [Online] [Cited: july 19, 2019.]

6. Allison Ramsey, MD. Allergy (Allergies). medicinet. [Online] [Cited: july 19, 2019.]

7. Nordqvist, Christian. Everything you need to know about allergies. medicalnewstoday. [Online] october 24, 2017. [Cited: july 19, 2019.]

8. allergies overview. webmd. [Online] [Cited: july 19, 2019.]

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Author: Ahaana Sahay