There are two types of food allergy: Immunoglobulin E (IgE) allergy and non-IgE allergy. The prevalence of food allergy is 1.2% to 3.2% in the adult population.

IgE allergy causes rapid reactions usually within minutes of ingestion of the food. In some cases this type of allergy can cause anaphylaxis eg. as seen in cases of peanut allergy. Patients with a history of anaphylaxis need to carry an adrenalin pen in case of a reaction. Tests for IgE allergy include validated IgE blood tests and skin prick tests (previously known as RAST).

Non-IgE allergy causes delayed reactions taking anywhere between one to 48 hours to materialise. This type of allergy does not cause anaphylaxis. It is believed that it is T or B cell related. However, this remains unknown. Most adults with a food allergy that affects their gut will have non-IgE food allergy. Currently there are no validated tests for non-IgE allergy. With non-IgE allergy it could be several hours or even days for reaction after ingestion. Therefore it can be difficult to diagnose. A trial of food exclusion followed by food challenge is used to help confirm and diagnose or rule out a food allergy. 

Symptoms of food allergy

Both types of food allergy can cause symptoms in the gut such as diarrhoea, bloating, nausea, constipation, wind and vomiting. Skin conditions such as eczema, itching, rashes, hives or respiratory symptoms of congestion, runny nose, dry cough, sneezing and itchy eyes can also be signs of allergy.

Additionally, some fruits and vegetables (eg. carrots, apple, plum, pineapple) will cause allergic symptoms in the mouth and throat for some patients with a history of hay fever. This food allergy is known as oral allergy syndrome. The body recognises the protein in fruit and believes that you are eating pollen and reactions occur. This allergy is not generally associated with severe reactions and cooking the fruit and vegetables before consumption breaks down the protein and will often prevent any reaction from occurring. 

Food Intolerance (non-immune mediated)

Although the terms are often incorrectly used interchangeably, a food intolerance is not the same as a food allergy.  In food intolerance the immune system is not involved and no allergic reaction takes place. The majority of patients have a non-immune mediated condition. There are no validated tests to diagnose food intolerance. The gold standard currently is food elimination and re-introduction with careful monitoring of symptoms.

Symptoms

Food intolerance symptoms usually involve the digestive system unlike food allergy which in addition to gastrointestinal symptoms can involve skin condition and respiratory symptoms.

Symptoms include pain and discomfort in the abdominal area, bloating, wind, reflux, diarrhoea/constipation, nausea.

Case study 1: Female with severe GI symptoms and queried food allergy

Presenting symptoms

The patient presented with vomiting, nausea, abdominal pain, migraines, low energy levels, worsening reflux and alternating diarrhoea/constipation, which was diagnosed as irritable bowel syndrome.

Infancy and childhood

In infancy the patient suffered from severe colic, back-arching, screaming, repeated vomiting and inability to settle.

In childhood, she presented with daily abdominal pain, regular vomiting, was regularly sent home from school, as well as having an ill father and moving house several times; she was told that she was attention seeking and suffering from anxiety.

Atopic background

• Mother had a history of cow’s milk protein allergy (CMPA)

• Hayfever; March/April, began in 30s

• Lip swelling and itchy mouth after eating cherries, pineapple, cantaloupe, melon and less ripe apples

• Mouth itching and stomach pain from under ripe banana and kiwi

• No latex allergy history

• Nausea, severe pain, diarrhoea and hard abdominal distenstion from Quorn

Coeliac symptoms

• Hypothyroid

• History of repeated low iron

• Borderline vitamin B12

• Reflux substantially worse since starting gluten free diet

• Gluten free diet slightly reduced muscle aches, migraines and energy levels

• Father reacted to gluten with increased reflux

• Negative CD bloods when eating gluten

Gastro tests

Calprotectin, colonoscopy and gastroscopy tests were all clear.

Taking a clinical history 

Taking a detailed history of symptoms and diet is the cornerstone of diagnosing and managing food allergy/intolerance.

It is essential to enquire about family history of allergies and to ‘join the dots’. To acquire a full detailed clinical history you must ensure that your questions are thorough:

• Are the symptoms present every day?

• How often does the patient have migraines?

• When did the hayfever start?

•  When did the patient’s mother develop CMPA? Some patients will themselves have no history of allergy but will have a very strong family history of allergies.

Tests

In the community there are no allergy tests, therefore the diagnosis is elimination and re-introduction. The re-introduction is the actual diagnosis as eliminating a food and reduction of symptoms can at times be coincidental, therefore it is the re-introduction and recurring of symptoms that confirms diagnosis. 

Rule out coeliac disease. It is very important to inform the patient that gluten needs to be in their diet for six weeks prior to a blood test for coeliac disease. Therefore, if the patient has already eliminated gluten from their diet the test will be inaccurate. Rule out other possible conditions using available tests such as calprotectin, colonoscopy and gastroscopy.

Allergy or irritable bowel syndrome

The immune system is more commonly activated in irritable bowel syndrome (IBS) than in healthy controls. This does not mean that every IBS patient has an allergy, however, there seems to be a subset of IBS patients for whom allergy is relevant. IBS patients have a history of atopy (asthma, eczema, hayfever). IBS patients with atopy are normally negative to traditional tests and this is because it is almost certainly non-IgE and not coming up in the test. Hayfever sufferers may cross react with certain vegetables and fruit causing IBS-type gastrointestinal (GI) symptoms (oral allergy syndrome mentioned previously). 

Key considerations 

• Negative coeliac

• Gastro tests negative

• Atopic mum with CMPA

• Diet is low in FODMAPs (from four-day diet history provided)

• Problems ongoing since infancy

As this patient is negative coeliac and diet is low in FODMAPs, the next step is to investigate the allergy side. GI allergies are often non-IgE which means there is no test and reactions are delayed, therefore it can be very difficult to prove and dietary elimination and re-introduction forms the diagnosis. Do not delve straight into a low FODMAP diet. If this patient’s mother had CMPA,  trial a dairy free diet.

Review consultation

When the patient returns for review, re-assess the score chart with the patient and compare before and after.  At four weeks post dairy-free diet, the patient reported the following:

• Within four days acid improved

• Within one week the patient was feeling considerably better

• Within four weeks the patient was feeling almost 100% better

• Two to three controllable stools per day

• Joint pains much improved

• Can now sleep better

• Enjoying food for the first time in years

• Can socialise with family and friends.

Reflux was one of the largest issues for this patient. This improved within four days of a dairy-free diet. This is a patient who had been feeling ill since birth and had a very low BMI as she had been avoiding most foods due to symptoms. Eating disorders are often suggested in these patients when in fact the cause is food allergy/intolerance. Joint pains had improved which is a very common improvement with food allergy patients. 

Score charts are extremely helpful as they are a very visual aid to monitor your patient’s symptoms. 

Non-coeliac gluten sensitivity (NCGS)

Gluten sensitivity shows higher levels of innate markers and some more adaptive immune markers than coeliac disease patients. Those with gluten sensitivity have more anxiety, depression, fatigue, IBS, food allergy and dairy intolerance than the general population but they do not appear to suffer to the same degree with anaemia, autoimmune history, low ferritin, folate or B12 as coeliac disease patients.

Gluten sensitivity studies consistently show that tiredness, headache/migraine and joint pain are common symptoms.

Diagnosis of gluten sensitivity

This condition is currently a diagnosis of exclusion. It is unknown whether long-term strict avoidance is necessary or whether the condition is transient.

To diagnose gluten sensitivity:

• Rule out coeliac disease

• Rule out wheat allergy

• Rule out fermentation (FODMAP)

• Gluten free diet response and gluten challenge.

Biochemical features of GS

• Coeliac tests – negative

• IgE allergy test – negative.

Anti-gliadin antibodies (AGA)

Serological analyses found AGA positivity in 40-50% of patients with gluten sensitivity. This figure is much lower than that of coeliac disease (80-90%), however much higher than in those with IBS (20%) or in the general population (2-8%). Therefore AGA positivity in the presence of clinical symptoms of gluten sensitivity (and in the absence of other tests which conclude negative for coeliac disease) can support diagnosis for gluten sensitivity. 

HLA typing 

The presence of HLA-DQ2 or DQ8 is found in approximately 95% of patients with coeliac disease and in approximately 40% of patients with gluten sensitivity. However, HLA-DQ2 and/or DQ8 positivity is found in the region of 30% of the population therefore HLA typing is not useful for NCGS diagnosis as the prevalence is not largely different to that of the general population. 

Mucosa in some patients appears to have a slight increase in immune cells, however this is very unclear and cannot be said for all patients.

Is NCGS due to gluten?

NCGS has been included in the nomenclature for gluten-related disorders but yet the underlying cause of NCGS is unclear. This is mainly because the offending dietary protein has not yet been identified. Gluten is a protein found in wheat, rye and barley. Although NCGS is triggered by gluten containing cereals, the offending protein could include components different from gluten itself such as the cereal protein amylase-tryptin inhibitors (ATIs). If this was the case it would exclude other cereals relevant such as barley and rye and perhaps a more correct terminology for the condition would then be non-coeliac wheat sensitivity? Or to distinguish it from FODMAP should we name it non-coeliac wheat protein sensitivity? 

What is emerging in some of the research is that some cases are improving because we are taking the FODMAP effect out and therefore it has nothing to do with gluten sensitivity – this is the cause of much debate currently.

Case study 2: Adult Female with GI and extra-intestinal symptoms

Presenting symptoms

• Bloating

• Abdominal pain

• Wind

• Gurgling

• Urgency

• Explosive diarrhoea 

• Nausea

• Reflux

• Repeated low iron and vitamin B12

• Negative CD bloods.

Extra-intestinal symptoms

• Numbness and tingling in hands and feet

• Speech issues

• Repeated mouth ulcers

• Balance issues

• Migraines/repeated headaches

•Hair thinning.

If there is no atopic background or family history of allergies (such as in this patient), then the patient is much less likely to have a food allergy. Many of these symptoms are similar to coeliac symptoms, however, the patient had a negative coeliac blood test. The presenting symptoms are also similar to IBS and these patients are often referred to a dietitian with IBS (note patient’s diet was low in FODMAPs but symptoms remained).

NCGS can easily be confused with IBS, however, symptoms outside the intestinal tract are often reported by NCGS patients (foggy mind, muscle and joint pain) which cannot be accounted for by FODMAPs intolerance. NCGS is a condition that results in intestinal and extra-intestinal symptoms. 

Treated for possible gluten sensitivity

The patient above embarked on a gluten-free diet and using the symptoms score chart it was reported that symptoms greatly improved. The patient reported ‘stools now normal and I feel much better’, ‘more energy’ and ‘hair thickening’.

Despite symptoms improving on removal of gluten from the diet, the exact diagnosis remains unclear. Does this patient have gluten ataxia (as certain symptoms suggest ataxia), gluten sensitivity or non-IgE wheat allergy? The exact diagnosis remains unknown.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder that affects the gut. It is a chronic condition that many people will need to manage on a long-term basis and can be debilitating for some. 

Symptoms include abdominal pain, bloating, diarrhoea, constipation, distension and/or gas.

The low FODMAP diet is a relatively new concept emerging for the management of IBS but it has been well researched and is gaining credibility.

What are FODMAPs?

The ‘FODMAP’ acronym is used to describe a group of short chain carbohydrates and sugar alcohols.

• F = Fermentable – capable of being converted to short chain fatty acids by intestinal bacteria

• O = Oligo-saccharides – Fructans, GOS (wheat, some fruit, vegetables, beans)

• D = Disaccharides – Lactose (milk)

• M = Mono-saccharides – Fructose (honey, sweeteners, mango) and

• P = Polyols – sugar alcohols (artificial sweeteners such as manitol/xylitol/maltitol/sorbitol, some fruits).

FODMAPs are poorly absorbed in the small intestine and when malabsorbed they have an osmotic effect – drawing fluid into the intestine causing diarrhoea. These dietary carbohydrates are rapidly fermentable by bacteria causing gas production and thus abdominal distension. Oligosaccharides and sugars are fermented more rapidly than polysaccharides (dietary fibre) because of their shorter chain length. This production of gas (methane) can also slow movement and lead to colonic distension in the bowel which leads to constipation. 

The low FODMAP diet now appears on the NICE guidelines for the management of IBS and in the British Dietetic Association IBS Guidelines. 

Case study 3: Query allergy/irritable bowel syndrome

Medical history

The patient’s history incuded:

• Anxiety

• Coeliac screen – negative

• Abdominal US – NAD

• Medication – Imodium.

The patient was first diagnosed with possible dairy allergy and placed on a dairy free diet. Diarrhoea, urgency and nausea disappeared and the patient felt much better, however the patient was still having a lot of symptoms in the ‘moderate’ category (abdominal pain, bloating, wind, acid regurgitation).

Further investigations and intervention:

Diet analysis showed a daily diet quite high in FODMAPs (FODMAP vegetables x 2, FODMAP fruit x 2, sugar free mints, 500ml apple juice).  This patient was placed on a low FODMAP diet and upon review the symptom score chart was used. Previous symptoms in the ‘moderate’ category had moved to the ‘mild’ category and diarrhoea, urgency and nausea remained in the ‘none’ category.

When re-assessing symptoms at a review consultation, you will rarely get all symptoms in the ‘none’ category with IBS patients. If so, then you have more than likely hit an allergy on the head by mistake. Reaching the ‘mild’ category makes a huge difference to quality of life. This dietary intervention used a combination approach (dairy free and low FODMAP) and the patient reported ‘I can now lead a normal life’.

Key messages

• Infancy and childhood – always investigate as part of clinical history

• Look at extra-intestinal symptoms, don’t look at just IBS symptoms

• Look at the family history – is there a genetic link there that can give you a bit of a hint?

• Consider the need for two diets. Do not just advise the FODMAP diet

• Keep an open mind. 

This report is based on a presentation by Marianne Williams, specialist dietitian, IBS and allergy gastroenterology, given at the recent annual INDI/Nutricia Medical Educational Symposium 

An e-learning module developed from this presentation, and from the other presentations from this recent INDI/Nutricia Medical event are now available.

 Log on to www.nutricia.ie/events/view/changing_trends_in_dietetics_healthcare