The Science Behind Allergic Reactions

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The concept of human immunity started gaining popularity in the early 1900s. In 1906, Viennese scientist Clemens Von Pirquet claimed that symptoms caused by infections were not just the outcome of the actions of microorganisms and their toxins, but also our body’s reaction to them. The term ‘Allergy’ is derived  from the Greek words ‘allos’ and ‘ergia’. Allos means ‘different’ and ergia means ‘action’. If exposed to foreign agents, the body produces antibodies. While ‘immunity’ protects our body, hypersensitivity may prove harmful for us. Allergic responses may change over time. 

An unsuitable immune response to an otherwise harmless substance in our environment is called allergy. They are common and affect millions of people across the globe. Some allergies can be more serious than others and occur as a result of different environmental factors. For example, nearly 400 million people in the world suffer from Hay fever. While drug allergies impact 10 percent of the world population, over 200 million people suffer from food allergies. 

An allergy occurs as a result of the mistake of our immune system. It happens if the body mistakes allergen/pet dander as harmful and initiates a type 2 response. T-helper cells stimulate the production of antibodies which are called immunoglobulin (lg) E molecules. As a result, histamine is produced causing inflammation. While most people require two exposures for developing allergic symptoms, in rare occasions a person develops allergic symptoms at the initial encounter!

Exposure and genetics play a vital role in the development of an allergy. A person is more likely to develop an allergy in case their parents are allergic. However the type of allergy does not transfer from parent to child. For example, if a person is allergic to pet dander, it is not necessary that his child suffers from the particular allergy. Instead, the child might develop food allergies. The reason behind this remains a mystery!

People are never born allergic. It happens with exposure to outside stimuli. A person might develop an allergy to medicines, insect-stings, dust mites, fungi and food items such as shellfish, milk and eggs. The severity of the allergy may differ. While allergies to dairy products and shellfish can be outgrown, allergy to nuts or pollen may last lifelong. 

Hyper-sterile environment is inhibiting our body from identifying harmful allergens from harmless ones. Global climate change is also said to be responsible for the rise in the number of allergies. The rising pollen and spore levels increase our exposure. The symptoms of pollen allergy include sneezing, rashes, vomiting, diarrhea and bloating. In very severe cases, the person may suffer from asthma and anaphylactic shock. 

Common Allergies

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Food: It affects roughly 6 percent of children and 4 percent of adults. You can develop an allergy to a particular food at any point. Shellfish, eggs, milk and fish are among the common ‘problem’ foods. Symptoms of a particular reaction mostly begin two hours after digestion. ‘Anaphylaxis’ may prove fatal if not treated promptly. The patient shall be administered a dose of epinephrine/adrenaline. 

Hay Fever/Allergic Rhinitis: Being the most common allergy, it occurs when exposed to pollen, dust mites or mold. The various symptoms include runny nose, itchy eyes, sneezing or asthma. It can be either seasonal or perennial.

Contact Dermatitis: Soaps, plants, shampoo, latex, and even metals can cause such allergic reactions. It happens when the skin comes into contact with an allergen. Reactions include rash, hives or eczema (in extreme cases).

Insect-Stings: It can be extremely dangerous. At least 100 deaths are recorded every year due to insect-stings. Wasps, yellow jackets, hornets, and fire ants are among the deadly insects. The symptoms of reaction include pain, swelling, itching or anaphylaxis.

Drugs:  Drug allergy is a major challenge in a medical setting. Patients tend to develop allergies towards penicillin, certain antibiotics, aspirin and chemotherapy drugs. Common symptoms include rash, wheezing, swelling and anaphylaxis.

An allergy test involves a skin test or a blood test. The results of a skin test will be usually available in a matter of 20 minutes. A blood test is mostly used in cases of eczema or psoriasis. It might take days or weeks to receive blood test results.



Epinephrine: Epinephrine/adrenaline is the most important treatment for anaphylaxis. It must be administered within minutes after the first sign of anaphylaxis for relaxing the airway muscles and tightening the blood vessels.

Medicines: Antihistamines and nasal corticosteroids help in reducing swelling and cure sneezing, runny nose and itching. Corticosteroid creams or ointments help in stopping the spread of rashes.

Immunotherapy: Immunotherapy can be delivered via injection or sublingually. In immunotherapy, an increasing dose of an allergen is administered over time, for decreasing one’s sensitivity to the allergen. Immunotherapy is effective in the treatment of allergic rhinitis or insect-sting allergies. It is important to consult an allergist before undergoing immunotherapy.

Aversion: The best treatment is to avoid the allergen altogether. It helps to a great extent in the case of food, drug and skin allergies.

Scientists shall continue their research and develop better treatment for allergic reactions.


Read more:United Nations

Check your knowledge

Answer) The term ‘Allergy’ is derived from the Greek words ‘allos’ and ‘ergia’. Allos means ‘different’ and ergia means ‘action’.

      Answer) The common allergies include food, hay fever, contact dermatitis, insect-sting and drug allergies. 

  Answer) Epinephrine, medicines, immunotherapy and aversion. 

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