Q: Can you desensitise yourself to a food intolerance?
A: Food intolerances, which the American Academy of Allergy, Asthma & Immunology defines as “difficulty digesting a particular food,” are different from food allergies and often resolve on their own.
Food allergies involve the immune system, whereas food intolerances generally do not.
Some food intolerances are well-understood. Tyramine in chocolate and cheeses, for example, can trigger migraine headaches in some people. Similarly, histamine in fish such as mackerel and tuna can cause nausea, vomiting and flushing. Sulphites in dried fruit and tartrazine in food dyes can cause asthma exacerbations.
But the cause of most food intolerances remains unknown.
In a British study of more than 10,000 patients, the foods most often associated with intolerances were chocolate, food additives, citrus fruits, fish, shellfish, milk, cheese, eggs and nuts.
The most common symptoms of these intolerances were hay fever, headaches, joint pain, itching, hives and stomach discomfort.
In the largest study to date, doctors studied the electronic health records of 2.7 million patients in Massachusetts. They found that 3.6% had at least one food intolerance or food allergy. The list of offending foods was similar to that of the British study.
But a caveat must be noted. In both studies the investigators were unable to discriminate between food intolerances and food allergies. Because the symptoms overlap extensively, one cannot differentiate intolerance from allergy without specialised testing.
Further complicating things, some foods can cause both intolerance and allergy. Cow’s milk is a good example. It can provoke bloating and diarrhoea in individuals with lactase deficiency — a food intolerance — and can cause wheezing and hives in those allergic to the beta-lacto globulin milk protein — a food allergy.
An elimination diet, in which the potentially offending food is removed from the diet, is usually the first step in diagnosing food intolerance. While elimination diets have not been studied systematically, resolution of symptoms upon withdrawal of the food in question strongly suggests a food intolerance.
Reintroducing an offending food is often possible. The British researchers were able to do this with most of the patients in their study without provoking serious reactions. But this should be done under a doctor’s care.
Because of the complexities and potential pitfalls in the diagnosis and treatment of food intolerance, one should seek guidance from a specialist, typically an allergist or a gastroenterologist, depending on the nature of one’s symptoms.