Updated 08 June 2017

Why do we develop allergies in adulthood?

Late-onset food allergies do happen, even if you’ve eaten that particular food your whole life without any problems.


Most health-adults have heard about food allergy, but don’t give it much thought since it mostly affects kids. Right? Not so, says Immunology and Allergy Specialist Consultant Dr Rita Mirakian at the London Allergy Clinic. Late-onset food allergies do happen, even if you’ve munched away at some food your whole life with no problems.

Stress may be a culprit 

She says it’s not easy to say why an allergy develops in later life, but speculates it may be linked to infections, illness and lifestyle, which can weaken our digestive systems. “Stress may also be a culprit, as well as airborne pollution or the many chemicals to which we're exposed on a daily basis.”

Read: Managing food allergies

Food allergy and food intolerance share some similar symptoms, but it’s important to know they are not the same thing, stresses the Allergy Society of South Africa (ALLSA).

Food sensitivity (intolerance) describes any adverse, but non-life threatening reaction to food or food additives.

Food allergy develops when your immune system has an abnormal reaction to one or more proteins in a specific food or food substance. It can be life threatening, as even a tiny morsel of a food can cause a serious whole-body allergic reaction called anaphylaxis within minutes of eating an offending food.

Anaphylaxis symptoms include breathing difficulties, swelling of the upper throat and/or tongue, a very rapid or irregular heartbeat, low blood pressure or cardiac arrest. It can be fatal if not treated promptly with an injection of epinephrine (adrenaline).

Anaphylaxis increasing

Dr Claudia Gray, a Cape Town- based allergologist (doctor that specialises in diagnosing and treating allergic conditions), says the most common allergenic foods according to prevalence studies are “cow’s milk, hen’s egg, peanut, tree nut, wheat, soya, fish and shellfish”.

Dr Gray adds that shellfish and nut allergies are the most common triggers of food-induced anaphylaxis in adults and there is “evidence that this potentially fatal response is increasing”.

Read: Risk factors for anaphylaxis

Right now, there’s no cure for food allergies, even though researchers are working on experimental treatments such as anti-IgE antibodies and oral tolerance induction (oral immunotherapy).

Can you prevent a food allergy?

Bottom line: The most effective prevention is to avoid the offending food!

It’s advisable to see a doctor with specialist knowledge of allergies (allergist or allergologist), who will diagnose you correctly and monitor you regularly. You’ll be referred to a dietitian, who wll educate you about food labelling, how to avoid hidden allergens in foods, find suitable substitutes and prescribe a balanced diet.

Read: The truth about food labels

Lastly, if your doctor has diagnosed a severe food allergy, make sure to wear a medical alert bracelet to inform others of your condition in case of emergency.

ALLSA outlines the two main types of food allergies:

  • IgE-mediated (immediate type) food allergies are the most common type. They typically show reactions within minutes to two hours of consuming the offending food. This mostly affects milk, hen’s eggs, peanuts and other nuts, fish, shellfish, soya and wheat.
  • Non-IgE mediated (delayed type) is most commonly related to soya and cow’s milk, but can affect many other solid foods. Because the reaction occurs hours to days after eating the allergen, it’s often more difficult to recognise or link to a specific food. Symptoms usually affect the digestive tract (i.e. diarrhoea, colic-type pain, severe reflux, vomiting and blood in the stool).

Individual allergic reactions vary widely. If you have a milder allergy, you can eat a fair portion before showing symptoms. However, those with a severe allergy may even react after a tiny amount, being kissed by someone who has just eaten the food or to air-borne particles of the offending food.

Read more:

Allergy alert

Allergy testing

How to read food labels


1.        S Afr Med J 2015;105(1):68-69. DOI:10.7196/SAMJ.9103 Epidemiology of IgE-mediated food allergy



4.        Food allergy presentation by Global Resources In Allergy (GLORIA), flagship program of the World Allergy Organization (WAO).




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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