Allergies and Intolerances

Have you ever wondered (while looking at the aisles in the supermarket and seeing those enticing attractive packaged food items) what this brouhaha – of foods being lactose-free, nut-free, gluten-free, etc., etc. – is all about?


Haven’t we all gasped in shock reading news about the child who needed to be rushed to the hospital and resuscitated because of him developing an acute reaction while trying out some new food?

Ever wondered how food (something so vital for our sustenance and survival) can cause such disastrous reactions? Let me introduce you to the murky world of food allergy and food intolerance.


What is the difference between being allergic to a food and being sensitive (or ‘intolerant’) to it?

Although used interchangeably (primarily due to ignorance), there is a world of difference between the two.

The difference lies primarily in the way the body responds to each of these two independent phenomena. The body responds to an ‘allergen’ (any substance causing allergy) by triggering the immune system. In case of food intolerance, however, it is the digestive system that plays a major role. Most studies clearly proclaim that food intolerance is way commoner than food allergy. While there may be overlap of some symptoms, one clear difference lies in the way they affect our body. Let’s delve deeper into each of these now.


Food allergy

Food allergies arise from sensitivity to chemical compounds (proteins) in food, even those which occur naturally in food. These are therefore more common in people with a genetic or hereditary predisposition. The body mistakes an ingredient in food (usually a protein) as hostile. This then causes the body’s defense mechanism (antibodies) to spring into action in response to this ‘allergen’.


What really happens during an allergic reaction to food

In the body’s repsonse to these proteins, there is IgE production (immunoglobulin E, a type of antibody that mediates inflammatory response). When food containing the ‘allergenic’ protein is ingested, these antibodies are activated and released along with other chemicals like histamine in an effort to fight the hostile invader and shoo it out of the body. Histamine by itself affects the respiratory tract, gastrointestinal tract, skin, and the cardiovascular system, and is the main chemical responsible for the symptoms caused.


Symptoms of food allergy

Allergic symptoms are caused by immediate inflammatory reaction locally (namely, in the digestive system) and systemically (skin, respiratory or circulatory systems) These can range from mild to severe. The amount of food needed to cause a reaction also varies from person to person. The symptoms to look out for are:

  1. Rash or hives
  2. Shortness of breath 
  3. Inability to speak or hoarseness of voice
  4. Nausea
  5. Stomach ache and cramps
  6. Itchy skin
  7. Airway swelling

Anaphylaxis is a potentially fatal allergic reaction causing multi system failure with sudden drop in blood pressure requiring immediate intravenous epinephrine administration. If very severe and not intervened in time, anaphylaxis can cause death.


Common Food Allergens

The most commonly known food allergens are nuts, eggs, shellfish, peanuts, milk, fish, and eggs (which is why it is advisable to avoid giving peanuts to children till the age of three).



Food Intolerance

What really happens if you’re intolerant to a certain food?

When someone is intolerant to a particular food ingredient, this ingredient causes irritation of the digestive system (the gut lining) and/or there is inability to properly digest or breakdown the food (due to absence of certain enzymes). Subsequently, the effects are usually limited locally (to the digestive system), leading to diarrhoea, vomiting, stomach ache or indigestion and constipation. There may be occasional systemic effects like headaches, etc.


Factors that contribute to food intolerance or sensitivity

  • In lactose-intolerance, the absence of the enzyme lactase (needed to break down lactose) is the main culprit.
  • Another category of products that may cause intolerance is the bevy of chemical ingredients added to food to enhance color, taste and protect against bacterial proliferation. These incude various dyes, monosodium glutamate a.k.a MSG (primarily responsible for the mouth-watering flavour and taste of Indian Chinese cuisine), and sulfites (which occur naturally in red wine, or are added artificially to food items for mold prevention). Spray-on sulfates used to preserve fruits and vegetables are somtimes responsible for food intolerance to fruit and vegetables. Similarly, food containing salicylates may trigger symptoms in people who are sensitive to aspirin (a medicinal compound belonging to the salicylate family).


Symptoms of food intolerance

Amongst others, the symptoms of food intolerance include:

  1. Nausea and vomiting 
  2. Heartburn
  3. Diarrhoea
  4. Stomach aches
  5. Abdominal bloating, gas and colic
  6. Headaches
  7. Irritability or nervousness

The most commonly encountered food intolerances are to lactose (found in milk and other dairy products), gluten (found in grains like wheat, rye, etc.), and certain other foods (including fruits and vegetables).


How to tell the difference between Food Allergy and Food Intolerance?

Food Allergies are –

  • Usually triggered by consumption of even a tiny amount of food containing the allergic ingredient.
  • Occurs every time the offending food is consumed.
  • The allergic reaction is immediate (and can be life threatening at times).
  • Self-assessment is easier because of the immediate reaction.
  • A person is rarely allergic to more than one or two food ingredients.
  • The allergic response, however, is known to persist lifelong in these patients, barring few rare cases where the children outgrow their allergy.
  • People with food allergies are strictly advised to avoid the offending food completely.

For food intolerances, on the other hand –

  • A person can be intolerant to multiple food types at the same time.
  • The body’s reaction is usually delayed (upto 72 hours after eating the offending food).
  • The response to intolerance generally ceases when the offending food leaves the system.
  • Self-assessment is therefore difficult, as symptoms develop late, and could be caused by any of the offending foods.
  • Often dose-related – people suffering from it may be asymptomatic unless they consume the offending food in larger quantities or too frequently.


Are food allergy and intolerance forms of food poisoning?

The answer is undeniably a NO.

Food poisoning is a health hazard caused by ingestion of food that is contaminated with harmful bacteria and toxins. Contaminated food is a big no-no for everyone. With a food allergy (or intolerance) on the other hand, the offending food is actually quite safe to consume for the majority of people. Unfortunately, it triggers an unhealthy reaction in a select few (and gains notoriety for that).


Diagnosis and Treatment of Food Allergies and Food Intolerance

While food allergy can be diagnosed by skin-prick test for IgE sensitivity, food intolerance is diagnosed with the help of blood tests for IgG  sensitivity. The validity of the tests is however debated. Multiple types of allergens can be tested together through an allergen screening test, but sometimes one may still miss out on the offending ‘allergen’.


Allergy can usually be treated with antihistaminics (in case of minor reaction) and intravenous epinephrine (in the case of anaphylaxis). Treatment should be undertaken only under medical supervision.

Elimination diet (by trial-and-error) is the most reliable method for treating food intolerance.


Author credits – Dr. Kavita Mehta Thukral


Kavita Mehta

Kavita Mehta

Hey there, I am Dr. Kavita Mehta Thukral, and I combine a doctor's mind with a writer's soul. I’m an expert on medical, nutrition and fitness sciences. And a student for life. I’m proud to be a Fitmag Author. Writing for Fitmag gives me the opportunity to present scientific facts in a way that will have the maximum outreach, and therefore, the maximum impact on the quality of human life. There is no eye-opener better than knowledge and experience. After all, what are we without knowledge? So read it all here at Fitmag. Wishing all of us a healthy body, mind and soul.