What Is an Allergic Reaction

Medically Reviewed by Dr. K on 18 March 2021

What Is an Allergic Reaction?

Some people sneeze uncontrollably. Some people get itchy hives or watery eyes. Still, regardless of the reaction, it all comes down to allergies.

You’re not alone if you suffer from allergies.

Although the issue may appear to begin in the nose or eyes, allergies are the product of an overactive immune system.

Understanding that these responses arise will help you maintain control and feel better.

Why It Happen

Your immune system has a critical role to play in protecting your body from harmful threats such as bacteria and viruses.

However, an allergy occurs as it overreacts to substances it should not.

Reactions may be triggered by peanuts, eggs, or pollen, for example, also known as allergens.

Antibodies are released by the immune system after a reaction. There are proteins that send a signal to cells that says, “Stop that substance!" The cells then release histamine and other substances, which trigger blood vessels to dilate and triggers allergic symptoms.

The antibodies have a singular goal. Each one is unique to a particular allergen. Which helps to explain why certain people are allergic to peanuts but not eggs.

Allergens will reach the body through the skin, eyes, nose, mouth, or stomach, among other areas. This will congest your sinuses, inflame your skin, make breathing difficult, and trigger stomach issues.

What are the common triggers?

Why do certain individuals suffer from severe allergies while others do not? Experts admit they don’t have all the answers, but they do believe that family history is essential.

Among the most common allergens are:

  • Animal dander
  • Bee stings
  • Medications – penicillin
  • Dust mites
  • Peanuts
  • Tree nuts
  • Fish
  • Shellfish
  • Eggs
  • Milk
  • Wheat 
  • Soy
  • Insect bites
  • Latex 
  • Nickel
  • Mold
  • Plants 
  • Pollen


Allergic reactions can vary from mild and uncomfortable to severe and even life-threatening. It all depends on how the body responds to the allergen and how much of it entered into your bloodstream.

If the allergy is serious, you can have anaphylaxis, which is a life-threatening reaction. Some situations are potentially life-threatening and need immediate treatment.

Here are some of the most common allergic reactions:

Hay fever – also known as allergic rhinitis, may lead to the following symptoms:

  • Runny or stuffy nose
  • Sneezing
  • Itchy eyes, nose or roof of mouth
  • Red, swollen, watery eyes – a condition known as allergic conjunctivitis

Food allergies: You can experience tingling sensations in your mouth. It’s possible that the tongue, lips, throat, or ears may swell. You may even get hives. Under the worst-case scenario, you may develop anaphylaxis and need immediate medical attention.

Eczema: It is a skin condition that is also known as atopic dermatitis. The majority of cases of eczema are not caused by allergies. However, when you’re around objects that trigger an allergic reaction, the condition will flare up. The immune system in your body responds abnormally to chemicals known as allergens, which are commonly harmless. Hives, coughing, swelling, sneezing, and a runny nose are also potential signs. Itching, redness, and peeling or flaking are all symptoms of it.

Medications: A rash, face swelling, or hives can occur if you are allergic to a medication. It’s possible that you’ll start wheezing. Anaphylaxis can occur in serious cases.

Stings: If you are allergic to bees or other insects, you can have the following symptoms:

  • Oedema – a wide region of swelling near the area that was stung
  • Hives or itching all over the body
  • Difficulty breathing, wheezing, chest tightness, or a cough

An extreme reaction to a sting, like some other allergies like food and medicine, may result in anaphylaxis.


The majority of patients with allergies only have mild to moderate symptoms, although extreme cases may result in anaphylaxis.

It’s a serious condition that could lead to shock in your body. The most common causes include food, medications, insect bites, or latex.

Up to 12 hours after the first anaphylactic reaction, a second one can occur.

Anaphylaxis signs may appear out of nowhere.

They will rapidly progress from a minor rash or runny nose to more severe issues including difficulty breathing, throat tightness, hives or swelling, nausea or vomiting, and fainting or dizziness. Some people’s hearts stop beating or their heartbeat becomes rapid.

If you’ve experienced previous attacks or that you’re at risk for anaphylaxis, your doctor might recommend medication that you or anyone else can administer. This drug is found in devices such as Adrenaclick, Auvi-Q, EpiPen, Symjepi, or a generic variant of an epinephrine auto-injector.

Always carry this with you and be mindful of your allergy triggers.

And if you’ve used the injection device, call 999 and head to the nearest hospital emergency department at the first sign of concern. And if you’re beginning to feel better, go in case the reaction is delayed, as you could still develop anaphylaxis at a later stage.


For mild to moderate allergic reactions, there are medication options available. Antihistamines and decongestants, as well as nasal sprays, may assist with some symptoms.

If you have allergic asthma, your doctor can recommend an inhaler to help you breathe easier. Alternatively, they can administer a special antibody to alleviate symptoms.

If removing your allergens and taking drugs doesn’t provide enough relief, your doctor can recommend allergy shots. Immunotherapy is a form of medicine that may help people with hay fever and allergic asthma.

Tablets that dissolve under the tongue are another form of immunotherapy.

An over-the-counter sinus medicine can help relieve your symptoms for sinusitis.

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