Basic Information Allergic Reaction

By Medically reviewed by Panel Perubatan Hello Doktor

Allergies happen when your innate immune system prevents harmless substances. These substances are called ”allergens”. You can inhale, eat, and touch allergens that cause a reaction. Some symptoms of an allergic reaction are sneezing, a runny nose or watery eyes. And these symptoms may lead you to a mild discomfort or even a severe one. Therefore, it’s important to prepare some basic information about allergic reactions.

Why do you get an allergic reaction?

The allergic reaction starts when you come into contact with substances that you inhale, swallow, or get on your skin. After that, your immune system overreacts by producing antibodies called Immunoglobulin E (IgE). These antibodies travel to cells that release histamine and other chemicals, causing an allergic reaction.

The reason, that some people experience allergies while others don’t, is not yet discovered. A family history of allergies is the single most important factor that can be inherited. This puts you at risk of developing allergic disease.

Environmental factors also increase the risk of developing allergies. Such as,

  • Repeated exposure to foreign substances (allergens)
  • Diet
  • Pollutants (tobacco smoke and exhaust fumes)


The symptoms of an allergic reaction can range from mild to severe. And most of them are mild.

If you have got a nasal or skin allergy, common symptoms include: itchy and watery eyes, sneezing, itchy and runny nose.

Food allergies can also cause stomach cramps, vomiting, and diarrhea.If an insect sting was the trigger, you will have swelling, redness, and pain where it stung you.

There are certain allergic reactions that can be life-threatening, called anaphylactic reactions. Without treatment, this kind of allergy can result in death within 15 minutes.

Types of Allergic Disease

  • Hay fever typically occurs in the spring, summer or fall. Symptoms include sneezing, stuffy or a runny nose and itching in the nose, eyes or on the roof of the mouth. If the symptoms are year-round, they may be caused by exposure to indoor allergens such as dust mites, indoor molds or pets.
  • Hives are defined by itchy, red bumps that can appear in clumps and be either large or small. The trigger of Hives is certain foods or medications.
  • Allergic conjunctivitis or eye allergy occurs when the eyes react to allergens with symptoms of reddening, itching, and swelling.
  • Asthma is a chronic lung disease characterized by coughing, chest tightness, shortness of breath and wheezing. When you experience asthma symptoms, your inflamed airways become narrowed, making it more difficult to breathe.
  • The food allergy will cause your innate immune system overreacts to a particular protein found in that food. Symptoms can appear when coming into contact with just a tiny amount of the food. Here are some common triggers: the proteins in cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts.
  • Rhinosinusitis, which is also commonly called sinusitis, causes nasal congestion, facial pressure, cough and thick nasal discharge. People with allergic rhinitis or asthma are more likely to suffer from chronic sinusitis. This is because the airways are more likely to become inflamed when allergic rhinitis or asthma is present.

Diagnosing and Treating Allergic Reactions

Your doctor will first examine if a reaction is allergic or not. The doctor will ask about your medical history and perform a physical exam. The doctor may also want to perform some of the following types of allergy test to determine which substance is causing your allergy:

  • Skin test involves applying a small amount of a suspected allergen to the skin and watching for a reaction.
  • Allergen-specific serum IgE test measures the blood level of IgE . IgE antibodies are unique to each allergen. Thus, checking for particular variants in the blood can help the doctor determine if an allergy is present.

Blood tests are sometimes done to detect a type of white blood cell called eosinophils. Eosinophils presents for everyone, but in the case of having allergic reactions, they are usually produced in greater numbers.

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Review Date: November 10, 2016 | Last Modified: December 19, 2019

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