Food Intolerance and Food Sensitivities

When there is an adverse reaction to food, but tests for an immune-response basis for the reaction are negative, the term ‘food intolerance’ is used to d scribe the condition.

Lactose intolerance is one of the most common kinds of intolerance. Many people are unable to produce an enzyme called lactase, which is needed to digest milk properly. Because they have a reduced ability to digest the sugar called lactose that is found in milk, these people report symptoms of bloating, wind, diarrhoea or other digestive problems after drinking milk. (It is important to note that other adverse reactions to dairy products, such as excess mucus, eczema and asthma, are an indication of a milk allergy rather than a lactose intolerance.)

One solution to lactose intolerance is to avoid all milk products. However, some people with this intolerance are able to consume dairy products as part of a meal containing some fat, as the fat slows down the release of the lactose from the stomach. Another solution is to treat milk with lactase drops or take lactase with milk.


A number of common health problems can be triggered by sensitivity to food. They include asthma, drowsiness, eczema, irritable bowel syndrome and migraine. If you think that you have a condition that may be linked to a food sensitivity, consult a family practitioner or nutritionist, who may refer you to a food specialist. It is important to find out which food is responsible for the adverse reaction and to try to eliminate that food from the diet.


This respiratory condition makes breathing difficult and can cause wheezing and coughing. The symptoms of asthma may be produced by a variety of triggers including anxiety, physical stress, chest infections, pollen, dust mites, smoke, animal hair and specific foods. Common foods that may trigger asthma include cow’s milk, wheat and other cereals, yeast and foods containing mould, such as blue cheeses. Nuts, peanuts (which are not nuts, but seeds), fish and eggs can produce the most immediate and dangerous reactions. Asthma sufferers who suspect that foods may be triggering attacks are advised to keep a food diary and seek expert help.


A food intolerance can make a person feel drowsy and lethargic. In many cases, the sufferer is sensitive to grains; wheat is a common culprit. The process of digesting wheat can have the effect of releasing chemicals in the brain that induce sleepiness. Excluding wheat from the diet can often improve health and boost energy levels.


There is some evidence to suggest that eczema, particularly in childhood, is linked to food allergy. The symptoms include redness, severe itching and dry, flaking skin. The main culprit foods are thought to be eggs, milk and other dairy products, as well as fish, shellfish, wheat, tomatoes, nuts, soya products and yeast. Some babies develop eczema when they are given formula milk for the first time. This may indicate a sensitivity to cow’s milk. People who have eczema are often advised to go on an elimination diet under expert supervision.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common digestive disorders. IBS has many symptoms, including wind, bloating, intestinal pain, diarrhoea and constipation. Food allergy or sensitivity is undoubtedly a common cause of IBS symptoms, because regular ingestion of an allergen can cause chronic inflammation of the bowel and diarrhoea. The resulting impairment of digestion can lead to gas formation.

For people with IBS, fatty or spicy foods, dairy products, alcohol and many fruits and vegetables can trigger symptoms. Dairy products and wheat have proved to be common triggers where IBS is concerned. Although doctors do not yet understand the cause of this condition, IBS is clearly also affected by factors other than food, including stress. Sufferers are advised to keep a diary of their diet, emotional state and symptoms, in order to form an idea of what triggers their attacks and then to try to eliminate allergens from their diet.


Migraine attacks are characterized by severe, disabling headaches, which are sometimes preceded by visual disturbances and often accompanied by nausea and vomiting. Possible triggers include stress, genetic factors, hormonal variations during the menstrual cycle, fatigue, a drop in blood-sugar levels, unstable levels of the brain chemical serotonin, sensor-related factors such as bright lights and loud noises, and certain foods. These triggers may cause migraines or increase sensitivity to migraine-triggering allergens. Migraine sufferers may find that keeping a diary helps them to pinpoint possible triggers.

Several foods are considered to be common triggers for migraine sufferers: cheese, chocolate, wine, citrus fruit and coffee. Other common triggers include other alcoholic drinks, shellfish, meat extracts, yeast extracts, stock cubes and nitrates in processed meats. It is thought that, in some people, migraines may be triggered by the tyramine (a derivative of the amino acid tyrosine) contained in cheese, chocolate, meat, yeast extracts and in some wines. Nutritionists can help people who suffer from migraines to try to identify foods that may be triggers so that they can avoid them. Migraine sufferers may also be advised to eat regular light meals in order to prevent a drop in blood-sugar levels.


Very young children, especially babies, are more susceptible to food sensitivity than adults. Common allergens for children include eggs, wheat, peanuts, fish, milk and soya beans. Surveys suggest that about one child in ten is affected – although eight out of ten affected children seem to grow out of the problem by the age of five.

Food sensitivity usually becomes apparent when babies are weaned from breast milk to formula, because the most common food sensitivity in the West is to cow’s milk. Milk and eggs are frequently the cause of childhood eczema. Any symptoms are usually relieved once the foods are excluded.

Foods that cause adverse reactions are often the first foods that babies encounter; researchers are trying to discover whether there is a link. It is possible that a baby may react badly to a food because its young digestive system cannot yet cope properly. Until more is known, some experts suggest that babies should not be given cow’s milk, soya or wheat until the age of six months.

Some substances, such as food additives, sugar, caffeine and salicylates (aspirin-like compounds that occur naturally in many foods, including most fruit and some vegetables), are thought by some people to be linked to childhood hyperactivity.

Often abbreviated to hyperactivity or ADD, attention deficit hyperactivity disorder is now affecting an increasing number of children. A hyperactive child displays disturbed and unpredictable behaviour, suddenly becoming aggressive or tearful, and acting in an impulsive or reckless manner. He may lack the ability to concentrate. Hyperactive children often have health problems, such as asthma and eczema.

Multiple factors have been implicated in hyperactivity and other behavioural changes in children. These include: an unstable home environment; exposure to environmental pollutants (for example, heavy metals such as aluminium, lead and copper); and learning difficulties associated with dyslexia, hearing problems and the need for glasses. Other factors are thought to be diet-related and include the consumption of artificial food additives (such as tartrazine, used in sweets, soft drinks, biscuits, cakes and jams); food allergies and sensitivities (some children, for example, react to salicylates); abnormal metabolism of sugars; and nutritional deficiencies (for example, insufficient iron, calcium, magnesium, zinc or essential fatty acids). It has also been found that caffeine in cola drinks and chocolate can cause childhood insomnia, and a tired child is more likely to experience problems with concentration.

Although the results of studies linking food additives and hyperactivity are not universally accepted (often because of lack of consistency in test conditions and criteria), some healthcare practitioners believe that there is a link between the consumption of these products and childhood hyperactivity.

Parents can test whether food is to blame for their child’s behaviour by cutting out foods that are common allergens, such as cow’s milk, highly processed foods containing additives and stimulants, such as biscuits, confectionery and brightly coloured soft drinks. This should be done under the guidance of a food specialist.