Immune reactions to food
Immune reactions to food
`When I finally found someone who could say what was wrong with me, it was such a relief. I can’t tell you how much ill-health and pain and misery I’d had up to that point. I’m immensely grateful to the doctor who sorted the problem out for me. My life has been transformed.’
Richard has eosinophilic gastroenteritis, one of the rarer immune reactions to food. Like all rare diseases, it can escape diagnosis for a long time. IgE (the allergy antibody – see box on p. 12) is sometimes involved in eosinophilic gastroenteritis, but it is not an essential part of the reaction. Those who, like Richard, do not make IgE antibodies to the problem food will not give positive skin-prick tests. For them, the possibility of food being responsible for their symptoms may well be overlooked*.
Another difficulty for patients such as Richard is that most of the non-IgE immune reactions to food affect babies and children exclusively. A few of them can also occur in adults, but this is very rare, so it’s not something that automatically springs to mind when the doctor is searching for a diagnosis.
Eosinophilic diseases
The key event in these diseases is the arrival of large numbers of immune cells called eosinophils (see p. 19) in the walls of the digestive system. If the eosinophils converge on the tube leading down to the stomach (the oesophagus) the disease is called eosinophilic oesophagitis, and the symptoms include reflux (regurgitation) of food, occasional vomiting, refusing food (in babies), stomach pain and disturbed sleep.
If the stomach is the focus for the eosinophils, this is eosinophilic gastritis, and there is vomiting, pain, poor appetite and therefore poor growth. There can also be obstruction of the stomach outlet which may, in a few babies, produce pyloric stenosis (the main symptom is projectile vomiting).
When eosinophils flock to the intestines as well as to the stomach, the disease is called eosinophilic gastroenteritis. In
terms of symptoms, the picture is not much different from the previous condition, but there can be diarrhoea as an additional symptom, and babies may be irritable and puffy in appearance.
These conditions are most common in babies, but sometimes they continue through childhood. Very occasionally they occur in adults too.
Heiner’s Syndrome
This disease affects babies only, and is very rare. It is a severe form of cow’s milk sensitivity leading to wheezing and haemosiderosis (bleeding into the lungs). The child usually seems sickly, growth is slow, and there may be recurrent bouts of pneumonia. A full diagnosis requires blood tests to check for anaemia, examination of sputum under the microscope, and a biopsy or lavage (see p. 92) from the lung. The only effective treatment is to remove cow’s milk from the diet completely. Needless to say, this must be done under full medical supervision.
Other reactions to food
The cause of these diseases is not fully understood, but the immune system is clearly involved.
Dietary protein entero-colitis syndrome
In babies, the symptoms begin with general irritability and vomiting between one and three hours after a feed. Unless the offending food – usually cow’s milk – is withdrawn promptly, there will be bloating, diarrhoea (usually containing blood), anaemia, and poor growth. Older children have similar symptoms, while adults suffer terrible nausea, plus stomach pains and vomiting.
Nickel in food
Nickel and other metals in food may cause immune reactions for those with sensitivity to such metals (see pp. 55-6). The symptoms are usually in the skin, but there can be a few digestive symptoms too.
Dietary protein enteropathy
The main symptom here is diarrhoea, usually very severe. Often babies vomit their feed as well. Most have little appetite, and if the offending food is not withdrawn they suffer from poor growth, anaemia and other signs of malnutrition. This is because damage to the lining of the gut prevents nutrients from being absorbed properly. Older children show similar symptoms.
Dietary protein proctitis
This is a far less severe problem. The babies with this disorder look healthy, but there is inflammation in the bowel and small amounts of blood are passed with the faeces.
Diagnosis
There are two aspects to diagnosis:
• what kind of disease is it?
• what food or foods are causing the reaction?
Your doctor will probably try to answer the first question by looking inside the digestive tract with special equipment (endoscopy) and by taking a small sample – a biopsy (see p. 92).
A blood sample may also be taken to look for raised levels of immune cells and antibodies. Skin-prick tests or RAST tests (see pp. 91-2) will be tried to rule out the possibility of true food allergy – and because IgE may play a small part in these other forms of food sensitivity (in the eosinophilic diseases, for example).
Often the tests yield no very clear answers, especially in babies, and an exact diagnosis is not possible. But failure to answer the first question does not mean that the second question should be ignored. Pinpointing the culprit food or foods is vital.
Identifying the food is easier the younger the child, simply because the range of foods eaten is so much smaller. Cow’s milk is the most common offender when the disease affects young children – particularly bottle-fed babies, since standard infant formula is made with cow’s milk. Your doctor will prescribe an alternative formula (see box on p. 66) for you to try. For older children and adults, an elimination diet will probably be required to identify the food concerned. Among young children, likely offenders include soya, egg, wheat, rice, chicken or fish. A simple elimination diet, similar to that used for atopic eczema (see p. 198) may be adequate. You must have full medical supervision for this.
In the case of eosinophilic reactions, skin-prick tests may help identify the foods concerned, but are usually of limited value, so an elimination diet is again necessary. Where adults are affected by eosinophilic diseases, sensitivity to several different foods is likely, so identifying the offending foods usually requires the most exacting form of elimination diet, using an elemental diet for the exclusion phase (see box on p. 196). The symptoms are very slow to disappear: it can take up to eight weeks of avoiding the foods before your ailing digestive tract recovers. Don’t give up too soon.
Treatment
Avoidance is the only way here. Special infant formula (see box on p. 66) is required for cow’s milk sensitivity in babies.
In the case of eosinophilic reactions, some doctors may use steroid tablets as an additional treatment, just for a few weeks, to get the inflammation under control. Some new studies show that the anti-leukotriene drugs (see p. 149) are very effective for eosinophilic gastroenteritis.
Controversial topics
According to some doctors, a reaction to food may, on rare occasions, produce vasculitis (inflammation of the blood vessels).
Vasculitis itself is a well-recognised condition. The blood vessels are damaged by inflammation, and become more leaky. Symptoms often begin with a general swelling (angioedema), and an outbreak of small red blotches deep in the skin — especially on the legs — where small amounts of blood have escaped. These blotches later turn purplish, then yellow, before fading. This type of rash is known as purpura. Sometimes there are larger emissions of blood, resulting in spontaneous bruising.
Many different conditions can cause vasculitis, but only a few doctors would agree that food sensitivity is one of them. The inflammation could be caused by circulating immune complexes containing food antigens bound to antibodies (see p. 13). There is evidence, in some patients, of a direct effect on the cells called platelets that cause blood to clot.
Equally controversial is the suggestion that food sensitivity can be the cause of trouble for some children with kidney disorders. Some research groups have found that a few children with certain kinds of kidney disease recover on an elemental diet (see box on p. 196). All those affected have a classical allergic disease such as asthma or atopic eczema as well, and they tend to be sensitive to several different foods, plus pollen or other airborne allergens. Circulating immune complexes might be involved here, but no one is sure.
Some cases of food-related rheumatoid arthritis and palindromic rheumatism (see p. 76) could be due to immune complexes involving food molecules becoming deposited in the joints, but it is not the mechanism in all, or even most, of those affected.