Like other allergies, a food allergy triggers an immune reaction that creates an inflammatory cascade to protect the body against a perceived threat (in this case, a harmless food substance). As part of this response, the body produces specific antibodies, which can be tested for.
Often, the reaction to a food allergy is swift. Within 30 minutes, the patient may show signs of tachycardia, urticaria or, in severe cases, anaphylaxis. IgE antibodies mediate these immediate allergic reactions.
In contrast, delayed food reactions (known as type III allergies) are mediated by IgG antibodies. The reaction may be more subtle and can occur anywhere from several hours to several days after ingestion. Symptoms may include reflux, bloating, headaches, joint pain or fatigue. As the Royal Children’s Hospital in Melbourne notes,
Common symptoms [of non-IgE mediated food allergies] include abdominal discomfort, vomiting and diarrhoea. In some cases, constipation or colic can be the presenting symptoms. The symptoms often take longer to develop (hours-days) rather than those of IgE-mediated food allergies which frequently occur within 5-30 minutes following food ingestion.
Patients may experience delayed food allergies as a result of eating cow’s milk, gluten, yeast, eggs, soybeans, nuts or certain vegetables.
Common conditions include:
- Cow’s milk protein intolerances:
- Food protein-induced allergic proctocolitis (FPIAP)
- Food protein-induced enteropathy
- Food protein-induced enterocolitis syndrome (FPIES).
Since everything a patient eats eventually reaches the gut, it is important to consider the gut microbiome and its role in food allergies.
The gut microbiome
The human gut microbiota is established in infancy and consists of a complex and dynamic population of microorganisms (bacteria, fungi and viruses) that play a crucial role in maintaining immune and metabolic homeostasis and protecting against pathogens.
Genetic and environmental factors shape the microbiome but one of the most important influences is diet. Distorted or depleted gut microbiota (dysbiosis) is implicated in the development of many inflammatory conditions.
The role of gut dysbiosis in the development of IgG food allergies
Gut dysbiosis plays a role in the development of IgG food allergies. Increased intestinal permeability (leaky gut syndrome) allows the passage of larger undigested proteins into the blood, triggering the release of IgG antibodies and contributing to inflammation.
Returning to a healthy gut microbiota requires the identification of triggering foods and consequent dietary modification that may need to be highly personalised in the case of patients with type III allergies.
What should GPs keep in mind when assessing patients with suspected allergies?
If a patient presents with persistent symptoms with no obvious cause such as headache, digestive discomfort, skin complaints, joint pain or weight gain, GPs are encouraged to consider testing for non-IgE mediated food allergies.
ImuPro ImuPro has been providing high standards of diagnostic testing to Australia & New Zealand since 2005. Our focus is on delayed IgG food intolerances (type III allergy).
To keep up to date with the latest developments in this field, we encourage you to join our growing Australian and international network of doctors and health practitioners and position yourself as an authority in the field of delayed IgG food allergies.
ImuPro will provide you with extensive material for your patients, as well as professional advice to assist in providing a high standard of quality care in this area.
This information is intended for healthcare professionals.