Sign in to your account

Don't have an account?

Create an account
This website uses cookies to ensure you get the best experience on our website. Learn more
Black medical doctor in a white coat and red stethoscope examining a patient on a ward. Our doctors on askawayhealth have years of clinical experience to provide top notch care.

Need to check your symptoms?

Use our symptom checker to help determine what your symptoms are and to ensure you get the help you need.

Check your symptoms


Request a reset

Don't have an account?

Create an account


Reset your password

Don't have an account?

Create an account


What is an Allergy??

October 3, 2019

Are you curious about what an allergy is? This post provides a clear definition of allergies and explains how they can affect your body.

Allergy is a very common medical condition. People may have an allergy to almost any food, chemical, drug or other materials. But what is an allergy, really?

Let’s take a closer look at the allergy definition in the article below:

Before and After photos of a lady of african background with an allergy reaction from hair dye

An allergy is your body’s response to a substance – usually a foreign body – that it does not agree with.

Allergies are very common; especially in children though they mostly outgrow them.

Food allergies are among the frequently occurring events in children.

‘Hypersensitivity’ and ‘reaction’ are words also used to describe the body’s reaction to the substance causing the allergy.

What Are ‘Allergens’?

Allergens are substances that cause or trigger an allergic reaction.

Sometimes we do not know what causes the reaction.

But allergens can include medicines, foods, fibre used in clothing, animal or animal hair, chemicals, dust, grass and tree pollen, cosmetics like makeup, hair dyes or henna, creams or household chemicals like soaps etc.

How Does an Allergy Happen?

Well, there are certain cells in the body that become stimulated when the body encounters an allergic substance, allergen or trigger.

These cells proceed to ‘react’ against the trigger giving rise to the allergy and the symptoms we see.

Most often, allergy reactions are mild; but occasionally, they can be very severe or even life-threatening.

Symptoms of Allergy

These can include:

  • Skin rash that is itchy and burning and can occur all over the body;
  • Runny nose, itchy and runny eyes, sneezing as happens in hay fever;
  • Swelling of the face, eyes, lips and tongue.

The most serious type of allergy is called an anaphylactic reaction.
It is a medical emergency where; as a result of severe sensitivity to a substance, the body has an overwhelming reaction, and its tissues go into ‘shock’ as a result.

The Symptoms of Anaphylactic Reaction:

In an anaphylactic reaction, things can happen very quickly.

The symptoms usually start soon after exposure to the trigger, such as an injection – during baby immunisation, for example; or a blood transfusion with an incorrect blood type.

Other examples could be following a Henna or hair dye application or if a person eats food, they are allergic to like peanuts, eggs or fish.

  • Fast heart rate
  • Sweating
  • Difficulty breathing or breathing very fast
  • Loss in colour (going pale)
  • Sudden onset of a quickly spreading rash
  • Tongue swelling
  • Swelling of the eyes, lips, throat
  • Feeling faint, sick, dizzy, a sense of urgency or disaster about to happen.

Other aspects of Anaphylaxis

Commonly people may have Anaphylactic reactions to:

  • Fish or shellfish
  • Peanuts or other types of nuts
  • Certain medicines  – antibiotics like penicillin, for example.

Such people who are known to suffer from anaphylactic reactions must carry an EpiPen.

An Epipen is an injection of Adrenaline that you always carry on your person.

You (or others around you) can give yourself the injection immediately if you start to have a serious allergy reaction.

Adrenaline immediately works to reverse the effects of the anaphylactic reaction.

Read here about dealing with Child Emergencies in school.

For less severe reactions, medicines called Antihistamines are used to counter the effect of the allergy.

This is because, critically, one of the chemicals created by the body after its exposure to a trigger is to form Histamine, and this chemical causes a lot of the symptoms we see.

Some Antihistamines can be purchased over the counter.

If you suspect that you (or your child) have an allergy, see your doctor to get diagnosed and advice on how to treat it, medicines to use and what to avoid.

Editing By AskAwayHealth Team


All AskAwayHealth articles are written by practising  Medical Practitioners on a wide range of healthcare conditions to provide evidence-based guidance and to help promote quality healthcare

The advice in our material is not meant to replace the management of your specific condition by a qualified healthcare practitioner.

To discuss your condition, please contact a health practitioner or reach us directly

Photo: Allergy effect from hair dye. Credit Source – Hairsimply

Share this blog article

On this page

Let us know what you think

Want to know how your comment data is processed? Learn more

Access over 600 resources & our monthly newsletter.

Askawayhealth 2023 grant recipient from European Union Development Fund

Askawayhealth, 2023 Award Recipient

Our educational content meets the standards set by the NHS in their Standard for Creating Health Content guidance.

Askawayhealth aims to deliver reliable and evidence based women's health, family health and sexual health information in a way that is easily relatable and easy for everyone to access.

Askawayhealth symptom Checker tool image

Utilize our complimentary symptom checker tool to gain more information about any uncertain symptoms you might have.