Adverse reactions to foods can cause both mild and severe health problems in a subset of the population. Immediate food allergies are known to affect 4% of the general population, where as general adverse reactions to food may affect a much higher proportion (>20%). The symptoms caused by the food reactions can be as mild as bloating but as severe as anaphylaxis. Conditions which may be caused or exacerbated by adverse food reactions include asthma, arthritis, irritable bowel syndrome (IBS), migraine, otitis media and skin rashes. A wide variety of more non-specific symptoms can be attributed to food sensitivities such as fatigue, headaches, and difficulty losing weight, food addictions and trouble concentrating.

Adverse food reactions include any abnormal reaction resulting from the ingestion of a food. They can be categorised as food allergies (with an immune response) or food sensitivities/intolerance. The existence and classification of food sensitivities have been controversial. These types of reactions are
difficult to diagnose because the time between consumption and response may be delayed (up to 2 days) and the symptoms are often subtle. In many cases ingestion of the offending food paradoxically masks the symptoms temporarily. Furthermore, multiple causes contribute to food sensitivities, making this area difficult to study.

Recently studies in atopic patients and IBS have been implemented to demonstrate the effectiveness of the IgG test. Dr Dixon, an ear, nose and throat specialist with 25 years of experience dealing with delayed food allergies has conducted one such study. He investigated 114 consecutive patients from his practice that had a positive history of delayed food allergies. Symptoms included nasal obstruction and congestion, diarrhoea, cramps, gas, throat clearing, asthma, itchy eyes and even ringing in ears. Foods that were consumed more than 2 times per week were tested, and patients were asked to eliminate the IgG positive ones from their diets.  

The most common IgG positive foods were found to be cow’s milk, tea, chocolate, banana and wheat. After these dietary changes were implemented the results obtained were very convincing. Over 71% of patients achieved >75% improvement in all of the reported symptoms. This also included chronic patients who had been unresponsive to other intensive therapies. Furthermore, more than half of these chronic patients achieved 90% relief, whilst amazingly one fifth obtained full recovery from symptoms. It was also noted that 11% of patients who came to the clinic for the assessment of inhalant allergies had IgG-related food allergies as the sole cause of their symptoms. 

In IBS, food elimination of IgG positive foods have also resulted in symptom resolution in at least four studies. Two 6 month investigations showed improvements in stool frequency, pain and quality of life scores (IBS-QOL). At the one year follow-up in the study by Drisko et al., adherence to the rotation diet, minimal IBS symptoms and a perception of control over the disorder was observed. These studies illustrate the usefulness of the IgG test system for both atopic and IBS patients. Furthermore, this in vitro system may be an appropriate test for all patients with suspected delayed food reactions.