top of page
  • Writer's pictureImogen Tingay

Allergies and Intolerances – Understanding the difference

Allergies and intolerances are common health concerns that affect a significant portion of the population. The UK has one of the highest prevalence of Allergic disorder with ~20% and rising of the population being affected. However, it is important to understand that not all adverse reactions to certain foods or substances are the same and may not always be an allergy. In this bog post, I’ll be outlining the differences between IgE-mediated allergies, non-IgE-mediated allergies, and intolerances. By understanding these distinctions, we can better identify and manage these conditions, leading to improved health and quality of life for everyone!


IgE-Mediated Allergies

IgE-mediated allergies, also known as immediate hypersensitivity reactions, are the most well-known type of allergic response. They occur when the immune system recognizes a specific allergen as harmful and releases immunoglobulin E (IgE) antibodies to combat it. This immune response triggers the release of histamine and other chemicals, leading to various symptoms.

Symptoms of IgE-mediated allergies often manifest rapidly, within minutes to hours after exposure to the allergen. Common examples include anaphylaxis, hives, itching, swelling, respiratory distress, and gastrointestinal issues. Peanut, tree nut, shellfish, and latex allergies are commonly associated with IgE-mediated reactions. I had all of these as a child but am now only mildly allergic to latex.

Diagnostic tests for IgE-mediated allergies involve skin prick tests, something that can be terribly unreliable but that’s for another blog post, or blood tests that detect the presence of specific IgE antibodies. Avoidance of the allergen is the primary method of managing this type of allergy as the reactions can be so severe. In severe cases, individuals may carry auto-injectable epinephrine (such as an EpiPen) to counteract life-threatening reactions e.g. Anaphylaxis.


Non-IgE-Mediated Allergies

Unlike IgE-mediated allergies, non-IgE-mediated allergies involve a delayed immune response. These allergies are typically cell-mediated or immune complex-mediated, and symptoms can take hours to days to appear after exposure to the allergen.

Cell-mediated allergies involve immune cells other than IgE, such as T-cells, which respond to the allergen. This type of reaction is commonly seen in contact dermatitis, where the skin becomes inflamed upon contact with an allergen like nickel or poison ivy. Symptoms may include redness, itching, swelling, and blisters.

Immune complex-mediated allergies occur when the immune system forms immune complexes with allergens, leading to inflammation. This type of response is often associated with drug allergies, such as those caused by penicillin or sulfa medications. Symptoms can range from rashes and joint pain to fever and organ involvement.

Diagnosing non-IgE-mediated allergies can be challenging as there are no reliable blood or skin tests available. Diagnosis is often based on clinical history, elimination diets, and food challenges. Avoidance of the trigger is crucial for managing non-IgE-mediated allergies, and in some cases, medication may be prescribed to alleviate symptoms.



Intolerances are different from allergies as they do not involve the immune system. They occur when the body has difficulty digesting or metabolizing a particular substance, leading to adverse reactions. Intolerances are often caused by deficiencies in enzymes or issues with absorption.

One common example is lactose intolerance, where the body lacks sufficient lactase enzyme to break down lactose, the sugar found in milk and dairy products. Symptoms of lactose intolerance include bloating, gas, diarrhoea, and abdominal pain. Other intolerances include fructose intolerance, gluten intolerance (celiac disease), and histamine intolerance.

Unlike allergies, intolerances typically do not cause severe or life-threatening reactions. Diagnosis is often based on symptom evaluation, elimination diets, and sometimes, medical tests such as lactose breath tests or biopsies for celiac disease. Managing intolerances usually involves avoiding or limiting the intake of the offending substance or using enzyme supplements to aid digestion.


In conclusion, understanding the distinctions between IgE-mediated allergies, non-IgE-mediated allergies, and intolerances is crucial for accurate diagnosis and effective management. IgE-mediated allergies trigger immediate immune responses, while non-IgE-mediated allergies involve delayed immune responses. On the other hand, intolerances are non-immune reactions caused by difficulties in digestion or metabolism.

If you suspect you have an allergy or intolerance, consult with a dietitian, allergist or immunologist for proper evaluation and diagnosis. By identifying the specific type of adverse reaction, you can take appropriate steps to manage your condition, avoid triggers, and improve your overall well-being.

Recent Posts

See All


bottom of page