Allergy

Updated 25 October 2017

What happens to my body during an allergic reaction?

The symptoms of different allergies are often quite similar. Let’s take a look at how your body reacts when you have an allergic reaction.

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When you come into contact with an allergen, it’s your immune system that reacts to the substance you’ve eaten, inhaled or touched.

Although your immune system produces five types of antibodies, allergies usually involve the IgE antibody. When you are allergic to a substance, your body forms IgE antibodies, which can result in a nasty reaction.

When it comes to different allergies, symptoms are often quite similar. Let’s take a look at what happens to your body when you have an allergic reaction.

1. Hives

Hives appear as itchy raised areas that are red, pink or skin-coloured. They can can vary in size and shape and often appear in batches on your face, or arms, hands, fingers, legs, feet and toes.

In the case of hives, your body releases histamine as a defence mechanism. When the histamine is released, tiny blood vessels under your skin leak fluid, which accumulates and causes the reaction.

Hives usually disappear within 24 hours.   

2. Runny or congested nose

Your nose has a busy job – it filters five to eight litres of air that pass through your nostrils every minute. But when an allergy affects your nose, your immune system goes into overdrive.

According to the Harvard Health Publications, mast cells in the nasal tissue release chemicals, such as histamine and leukotrines, to fight the allergen.

The blood vessels in your nasal passage may swell, which causes congestion, and mucus production increases, which causes that runny nose.

3. Digestive issues

The Cleveland Clinic says that when you're allergic to a food, your body identifies an ingredient – often a protein – as a threat. An allergic reaction occurs when the antibodies struggle to “invade” this food. 

Your digestive tract needs to “rapidly get rid of or neutralise the irritant or the allergen. Common gastrointestinal reactions are abdominal pain, nausea, vomiting and diarrhoea,” Dr Lisa Pichney told Everyday Health

According to the American College of Allergy, Asthma & Immunology, most food-related symptoms occur within two hours of ingestion, but often within minutes. In rare cases, an allergic reaction can be delayed by between four and six hours, and sometimes even longer.

4. Anaphylactic shock

In severe cases, an allergy can cause anaphylactic shock. This reaction can affect your entire body. Anaphylactic shock can cause swelling of your throat and tongue; shortness of breath; difficulty breathing; an abnormal heart rate; a drastic drop in blood pressure; digestive issues; and itchy, red skin.

The most common anaphylactic reactions are to medications, latex, food and insect stings. In extreme situations anaphylaxis can be life threatening and must be treated without delay. 

First aid tips for anaphylactic shock

  • Check to see if the person is wearing an allergy bracelet so you can identify the allergy. If they are not and can talk, ask them what they’re allergic to. If they are carrying an EpiPen or asthma pump, help them find it and use it.
  • If the person is conscious, help them into a sitting position, which will make it easier to breathe. Encourage them to take slow, deep breaths.
  • If possible, give them an antihistamine.
  • If treatment doesn't help, call an ambulance or take them to a hospital immediately.

Image credit: iStock

 

Ask the Expert

Allergy expert

Dr Morris is the Principal Allergist at the Cape Town and Johannesburg Allergy Clinics with postgraduate diplomas in Allergology, Dermatology, Paediatrics and Family Medicine dealing with both adult and childhood allergies.

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