Asthma Chest & Allergy Centre

A centre of excellence providing treatment of Asthma, Allergies and Chest Diseases since 1992

Food allergy

Q.What is food allergy?
A.It is the appearance of some unpleasant symptoms in a sensitive (allergic) person after taking a particular food. The same food ordinarily causes no such symptoms in the vast majority of people who take it.

Q.What are the symptoms noticed in food allergy?
A.The symptoms may pertain to the gastrointestinal tract, the skin, the lungs or the whole body. There may be itching rash around the mouth, swelling of the lips, sores inside the mouth, vomiting, gaseous distension, or diarrhoea. The commonest skin reaction is urticaria (hives) in which red, itchy swollen patches appear in the skin. They arise suddenly in clusters in one area and disappear quickly from there to reappear in another area. Lung reactions in the form of asthma are uncommon as part of the food allergy.

Sometimes, food allergy manifests in the form of severe anaphylactic reaction with breathlessness, cyanosis (bluishness) and unconsciousness. If quick relief is not provided, it can be fatal.

Q.How long after taking the offending food, do the symptoms of food allergy appear?
A.The symptoms of food allergy may appear soon after taking it or may appear several hours later; in the latter case, it becomes difficult to identify the offending article of diet.

The same food in one particular season may produce symptoms, while in others, it may not. This depends on the combination with other allergic factors.

Q.Which foods cause allergy reactions more commonly ?
A.Food which cause allergic reactions include fish, prawns, oysters, lobsters, eggs, chocolate, cow’s milk, peanuts, soyabeans, dry fruits, citrus, etc. The parts of food that cause allergic reaction, are usually proteins.

Q.What are the characteristics of fish allergy?
A.Fish and other sea foods are amongst the most potent allergic agents. Those who develop reactions on eating fish should avoid other sea foods as well. Even the smell of fish can produce urticaria in some people who are strongly allergic to it.

Q.What are the characteristics of egg allergy?
A.White of an egg is pure albumin (protein), and a potent source of allergy. Taking a raw egg by a person allergic to it, can cause a severe reaction. Even the smell of egg’s content can cause allergic reactions in highly sensitive people.

Q.What are the characteristics of cow’s milk allergy?
A.It is seen more often in infants; 1 in 200 infants are said to be allergic to cow’s milk.

The symptoms produced are varied: from being unwell after taking cow’s milk to sores around the mouth, vomiting, diarrhoea, urticaria, eczema rash on the face or difficulty in breathing.

Q.What are the characteristics of wheat allergy?
A.An infant may develop a rash, abdominal colic or diarrhoea when it is given a cereal for the first time.
An older child or an adult may have asthma or a patch of eczema which is found to be improved by not taking wheat in any form.

Q.Are all reactions to food in infants and children allergic in nature.
A.That may not be so. Rash around the mouth in some children may be due to acid in foods like fruit juice. It is non-allergic in nature and usually a temporary problem.
Other reactions may be due to the presence of various preservatives in the commercial foods.

As the child grows older, even the foods which previously caused allergic reactions may be tolerated, perhaps, because of the maturing immune system.

Q.What is cross allergy to food?
A.All foods belong either to vegetable source or animal source and in either case they are grouped in families. Peas, soya beans, kidney beans, peanuts, etc. are all members of the pea (legume) family, just as garlic, onion, asparagus, belong to lily family. Similarly, many of the sea foods belong to one family.

Allergy to one member of a family may result in the person being allergic to other members of the same family. This is called cross allergy. Knowledge about this,fore-warns a person as to which foods to avoid.

Q.Is a person allergic to egg, allergic to chicken as well?
A.Usually not, Albumin, the pure protein in the egg, does not exist in the chicken.

Q.Is a person allergic to cow’s milk also allergic to beef?
A.Cooking usually reduces the ability of proteins in the food to cause allergic reactions. But some reactions may still occur. Boiled milk and cooked eggs still cause some reactions.

Q.How can one diagnose the allergy-causingfood?
A.Diagnosis as to which food is causing allergic symptoms is, many a time, like investigating a murder case with hardly any obvious clues. The difficulty is compounded when the offending food is either milk, egg or wheat, each of which is a common ingredient of many other foods, and its presence is not generally suspected by the patient. A thorough history of the patient is of the greatest help.

Skin tests in food allergy are not of much help. This is because the tests are done with foods extracted in the raw state but they are eaten in the cooked state. Many a time, there is no correlation between the skin tests and the trials with foods.

Blood tests are equally unreliable.

Food elimination tests are helpful. The patient is instructed to note in his diary, all the food he takes and the symptoms, if any, produced. By studying these daily notes for two to three weeks, one can often detect the onset of symptoms after taking a new food or after repeated use of a certain food. The elimination of these foods from the diet one by one results in disappearance of the symptoms, just as the intentional ingestion is followed by symptoms.

Even after carrying out all the investigations, sometimes one is not sure of the food causing allergic symptoms.

Q.How is a case of food allergy treated?
A.The best method of treating food allergy is to find out the incriminating food and to avoid it. While eliminating one food, it is necessary that a non-allergic substitute of equivalent food value, be added to maintain nutrition and avoid monotony. Along with this, the patient is advised to take as far as possible, cooked foods, which being denatured, cause less allergy.

Whenever possible, the infant should bebreast-fed. This reduces the chances of development of allergic symptoms. Giving of cow’s milk should be delayed upto the age of nine months to a year in a potentially allergic child. Milk prepared from the soyabeans is a good substitute. Soyabean milk should be given upto a year or so and then a re-trialmade with the offending milk. If only a few symptoms appear, then the cow’s milk may be gradually added in the diet. Soyabean milk is as nutritious as the mother’s milk; however, this needs to be supplemented with vitamins and minerals.

Injections of the incriminating foods are both dangerous and useless.

Those who are highly allergic to some foods, must carry epinephrine (adrenalin) and should be taught how to inject themselves with it, when necessary. Such people should also wear an identification bracelet which describes their allergy.

Q.What is food intolerance and how does it differ from food allergy?
A.Food intolerance reactions are caused by factors in the diet other than proteins. A common food intolerance reaction is the result of the body’s inability to properly digest milk sugar, lactose; this gives rise to diarrhoea and increasing weakness.

Food additives and preservatives are some of the other factors that cause reactions that are not really allergic but look like it. The food dye tartrazine has been shown to causeasthma-like symptoms in some persons. Sulphite preservatives such as sodium and potassium sulphite, bisulphite and metabisulphite are known to have the potential to cause a serious attack in some sulphite-sensitiveasthma patients. Sulphites are used in some restaurants as “stay fresh” agents, particularly as chemicals sprayed on salads to prevent wilting. They are also found in some processed foods and beverages like fresh shrimp, mushrooms, potato chips, dried fruits and wines.

Since reactions to these chemical can be very severe, people taking food outside their home frequently, should be aware of this problem.