Understanding Food Allergies and Intolerances

Food allergies and intolerances affect millions of people worldwide, impacting their quality of life and necessitating careful attention to dietary choices. Despite their prevalence, there’s often confusion about the differences between food allergies and intolerances, their symptoms, causes, diagnosis, and management strategies. In this comprehensive guide, we’ll delve into the intricacies of food allergies and intolerances, shedding light on these conditions to empower individuals with knowledge for better management and improved well-being.

Section 1: Differentiating Between Food Allergies and Intolerances

1.1 Defining Food Allergies:

  • What is a food allergy?

An adverse or potentially hazardous immune system response occurs following the consumption of a particular food. The exact cause of food allergies remains unclear. Occasionally, allergies that manifest during childhood may resolve as individuals reach adulthood. Symptoms of a reaction may encompass digestive disturbances, hives, or airway inflammation. In severe cases, reactions can pose life-threatening risks. Mild reactions are typically managed with antihistamine medications, while severe reactions necessitate immediate administration of epinephrine and emergency medical attention.

  • Immune system response: IgE-mediated reaction
  • Common food allergens: peanuts, tree nuts, shellfish, eggs, milk, wheat, soy,      fish
  • Symptoms: hives, itching, swelling, difficulty breathing, anaphylaxis
  • Diagnosis: skin prick test, blood test, oral food challenge

1.2 Understanding Food Intolerances:

  • Definition and mechanism

When someone struggles to digest a specific food, it results in a food intolerance or sensitivity, which may manifest as symptoms like intestinal gas, abdominal pain, or diarrhea. Often, people mistake a food intolerance for a food allergy, but they’re distinct: food intolerances affect the digestive system, while food allergies involve the immune system. Unlike food intolerances, food allergies can trigger severe or life-threatening reactions, known as anaphylaxis, even with tiny amounts of the allergenic food.

  • Non-immune responses: enzyme deficiencies, sensitivity to food additives, histamine intolerance
  • Common intolerances: lactose intolerance, gluten intolerance (non-celiac gluten sensitivity), fructose intolerance, histamine intolerance
  • Symptoms: gastrointestinal discomfort, bloating, diarrhea, headache, skin rashes
  • Diagnosis: elimination diet, hydrogen breath test, lactose tolerance test

Section 2: Causes and Risk Factors

2.1 Causes of Food Allergies:

  • Genetic predisposition

While there may be a genetic aspect to food allergies, susceptibility to allergies seems to stem from a combination of genetic predisposition and environmental factors. It’s crucial to recognize that allergies within families might also arise from shared environmental conditions that contribute to the emergence of food allergies.

  • Early exposure to allergenic foods

In 2019, a fresh examination of data from the EAT study revealed that the early introduction of allergenic foods offered protective effects against food allergies in certain high-risk children. The study compared the outcomes of early introduction and exclusive breastfeeding in infants who exhibited sensitization to one or more of the six featured foods (milk, peanut, egg, sesame, fish, and wheat) at 3 months of age. Sensitization indicated a heightened risk of developing a food allergy, as indicated by blood tests detecting allergy-related IgE antibodies to at least one of the six foods. While IgE antibodies are central to allergic reactions, it’s plausible to possess IgE antibodies against a food protein without experiencing a reaction upon consuming the food.

  • Environmental factors: pollution, hygiene hypothesis

Exposure to environmental allergens like grass or pollen allergens, whether through inhalation or skin contact, could potentially sensitize the immune system to be more responsive to protein families shared with food allergens.
Other exposures of concern include inadequate sunlight, endocrine-disrupting chemicals, pesticides, and certain pharmaceutical agents that could potentially influence or alter the risk of developing food allergies. Although research on this topic has been limited in both quantity and quality, numerous new epidemiological associations and experimental findings have bolstered support for this concept.

  • Cross-reactivity and oral allergy syndrome

Oral allergy syndrome (OAS) arises due to cross-reactivity between proteins found in fresh fruits, vegetables, and nuts with pollens. This condition affects a considerable proportion (up to 70 percent) of individuals with pollen allergies. The proteins responsible for triggering OAS symptoms in fruits and vegetables can often be neutralized through cooking or processing.

2.2 Causes of Food Intolerances:

  • Enzyme deficiencies: lactase deficiency (lactose intolerance), sucrase-isomaltase deficiency (sucrose intolerance)

In adults, disaccharidase deficiency leads to carbohydrate malabsorption, manifesting in symptoms that closely resemble those of irritable bowel syndrome (IBS).

Disaccharidase deficiency in adults is more prevalent than previously understood, encompassing lactase, sucrase, maltase, and isomaltase enzymes. These enzymes, produced by the intestinal brush border, play a crucial role in breaking down and absorbing carbohydrates. Deficiencies in disaccharidases can disrupt this process, leading to symptoms such as abdominal pain, gas, bloating, and diarrhea.

  • Sensitivity to food additives: sulfites, MSG

A sudden and rapid onset of symptoms, including flushing, bronchospasm, and hypotension, indicates a sulfite reaction. Conversely, experiencing burning, pressure, tightness, or numbness in the face, neck, and upper chest after consuming Chinese food (and other condiments such as salad dressings) suggests an adverse reaction to MSG.

  • Histamine intolerance: impaired histamine metabolism

Histamine intolerance, also known as enteral histaminosis or sensitivity to dietary histamine, is characterized by a condition wherein there’s a diminished capacity to degrade histamine in the intestine due to impaired DAO activity. This results in the accumulation of histamine in the bloodstream, giving rise to adverse effects.

2.3 Risk Factors for Food Allergies and Intolerances:

  • Family history of allergies or autoimmune conditions
  • Personal history of allergies or asthma
  • Age: infancy and early childhood for allergies, adulthood for intolerances
  • Environmental factors: exposure to allergens, gut microbiota composition

Section 3: Diagnosis and Management Strategies

3.1 Diagnosis of Food Allergies:

  • Clinical history and physical examination
  • Allergy testing: skin prick test, blood test (specific IgE), oral food challenge
  • Keeping a food diary

3.2 Diagnosis of Food Intolerances:

  • Symptom assessment and elimination diet

Inquiries into symptoms after food ingestion such as diarrhea, bloating, swelling or itching in throat. Foods are eliminated based on reported symptoms to identify trigger foods.

  • Specific diagnostic tests: hydrogen breath test, lactose tolerance test, histamine intolerance test

3.3 Management of Food Allergies:

  • Strict avoidance of allergenic foods
  • Reading food labels and identifying hidden allergens

When examining a food label, it’s advisable to begin with the “contains” statement. This section is mandated by the Food Allergen Labeling and Consumer Protection Act (FALCPA) of 2004, offering clear guidance to identify the most prevalent allergenic foods among Americans in straightforward language. For instance, the “contains” label should specify “contains milk,” or the ingredient list should indicate “sodium caseinate (milk)” rather than simply “sodium caseinate.” The FASTER Act of 2021 (Food Allergy Safety, Treatment, Education, and Research) expands the scope of FALCPA to include sesame as a common food allergen.

  • Emergency preparedness: carrying epinephrine auto-injectors
  • Education and awareness: informing family, friends, and caregivers
  • Regular follow-up with healthcare providers

3.4 Management of Food Intolerances:

  • Avoidance of trigger foods
  • Enzyme replacement therapy

Lactase supplements for lactose intolerance or PERT (pancreatic enzyme replacement therapy) which includes amylase, lipase and protease. It helps break down carbs, fats, and proteins. PERT is prescribed by a medical professional though over-the-counter digestive enzymes can also be purchased.

  • Dietary modifications: low-FODMAP diet for irritable bowel syndrome (IBS)

The low FODMAP diet restricts the intake of foods rich in FODMAPs, which are fermentable carbohydrates commonly found in various foods. Fermentation of these FODMAPs by gut bacteria, leading to gas production, is a normal aspect of the digestive process. FODMAP foods that aggravate the gut, including Dairy-based milk, yogurt and ice cream. Wheat-based products such as cereal, bread and crackers. Beans and lentils.

  • Addressing underlying conditions: treating small intestinal bacterial overgrowth (SIBO)

SIBO, or Small Intestinal Bacterial Overgrowth, refers to a condition characterized by an elevation in the quantity and/or changes in the composition of bacteria in the upper gastrointestinal tract. Symptoms associated with SIBO include bloating, diarrhea, difficulties in nutrient absorption, weight loss, and malnutrition.
The general nature of these symptoms makes it challenging to clinically differentiate SIBO from other conditions, such as IBS, lactose intolerance, or fructose intolerance.

Section 4: Living with Food Allergies and Intolerances

4.1 Nutritional Considerations:

  • Ensuring adequate nutrient intake despite dietary restrictions

Consulting a Registered Dietitian to determine what foods or supplements would be beneficial based on individual needs.

  • Substituting allergenic or trigger foods with safe alternatives

Common allergy trigger foods and their alternatives:

  1. Peanuts and tree nuts: Sunflower or pumpkin seeds
  2. Eggs (for baking): Unsweetened applesauce, mashed banana, vegetable oil
  3. Cow’s milk:  Rice, almond, coconut, cashew, hemp, and pea milk
  4. Wheat and sesame: Rice, corn, millet, potato, tapioca, and quinoa, coconut flour, spelt
  5. Fish and Shellfish: Lentils, black beans, red meat (preferably from strictly grass-fed animals or natural grain free diet)
  6. Soy: Lentils and Quinoa
  • Consulting with a registered dietitian for meal planning and nutritional guidance.

4.2 Psychosocial Impact:

  • Addressing emotional aspects: anxiety, fear, social isolation
  • Educating peers, classmates, and colleagues about food allergies and intolerances
  • Promoting inclusivity and understanding in social settings


Food allergies and intolerances pose significant challenges to individuals affected by these conditions, requiring diligence, awareness, and support for effective management. By understanding the differences between food allergies and intolerances, recognizing their causes and symptoms, and implementing appropriate diagnostic and management strategies, individuals can navigate their dietary restrictions with confidence and lead fulfilling lives. Empowered with knowledge and equipped with resources, those with food allergies and intolerances can embrace a lifestyle that prioritizes health, safety, and well-being.




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