Most of us gobble food without much thought as long as it appeals to our palate. But there are some who need to think before they eat—not because they dislike a food, but because it harms them. This forms the basis of food allergy, which in simple words is an exaggerated reaction of the immune system to an otherwise ordinary harmless food. As noted cardiac physician and allergologist, Dr Pramod Niphadkar says, "Food allergies are a part of life." Each one of us knows at least one person who reacts to a certain food. The reaction might be as simple as a minor rash or tummy discomfort, or a more complicated one that needs immediate medical attention. The more we know about it, the better it is for us.
An allergy is an inappropriate response [leading to troublesome symptoms] of the immune system to a substance, that in most people, causes no response at all. Such a substance is called an allergen; it provokes the immune system to produce specific antibodies, belonging to a type called Immunoglobulin E [IgE]. The IgE release histamines, which are chemicals that trigger allergic responses. The response could be instant or delayed, and can vary from mild to fatal.
About food allergies
In food allergies, the allergen comes from a food source. This allergen is mainly protein in nature, so the sources too are high in protein content. Take eggs for instance. Eggs are one of the commonest causes of food allergy—a normal hen's egg has various proteins, many of which are very allergenic such as ovalbumin, ovotransfferin or lysozyme. Another example is casein, which accounts for almost 80 per cent of milk protein and is a known allergen. One more leading cause of food allergy is the protein-rich seafood and shellfish. Mushrooms, peanuts, sesame, soy, chicken, coffee, chocolates, alcoholic beverages, tomatoes, fruits, nuts and wheat are other common sources.
The above list is universal. But dals and legumes are important allergy triggers specific to India, according to Dr Niphadkar. For most of us dal-chawal, chole-puri, rajma- chawal, or hot pakoras on a wet, rainy day are comfort foods—unfortunately, it's not so for a small part of our population. Chana or chickpea leads the allergy triggers list; in some cases even inhaling vapours of it being cooked has led to medical emergencies. Another causative is the gram dal or besan as we know it, while others include moong, tuvar and masoor dals, and fenugreek or methi.
Though the above foods are notorious for causing allergies, food allergy is mostly individual. Anyone could be allergic to just about any food, not just to these. Further, often these allergies tend to run in families passed down from generation to generation.
The allergic response to a food could be immediate [even minutes post-ingestion] or after a few hours, that is after digestion of the particular food. Red, swollen, itchy patches called hives or urticaria, that last no more than a few hours are one of most common immediate reactions. A few symptoms oscillate between both the above responses. Gastrointestinal related vomiting, diarrhoea, abdominal cramps and loud bowel sounds are some other usual reactions. Tingling in mouth and throat, swollen lips, wheezing, hay fever, headaches, breathing difficulty, asthma and inflammation of the eye are some other. The worst allergic response of all is an anaphylactic shock that could cause an itchy rash, pain in abdomen, diarrhoea, swelling of tongue and throat, shortness of breath, light-headedness and sneezing and in more severe cases a drop in pressure and unconsciousness. This needs instant medical attention, as it could be fatal.
A few allergic reactions such as atopic dermatitis or eczema, a condition in which the skin gets itchy, scaly and red could be chronic. It arises mostly due to personal or family history of allergy.
Infants and children too show reactions to food, however, in most cases, the reactions wane as the child grows and its immune system develops. If it does continue though, consult the doctor. Babies often react to eggs and wheat; a few develop a red rash around the mouth after eating an orange or a tomato, while others might have abdominal pain after consuming milk.
Catching the culprit
Things to do if you think you may be allergic to certain foods.
- Consult an allergologist if you feel you are reacting to some food. He will go through your personal and family history, kinds of food eaten, frequency, and nature of symptoms.
- Get an Allergy Skin Test done, in form of prick or scratch through which the doubtful foods are introduced [usually hives develop within 20 minutes if ittests positive].
- Ask your doctor if you require undergoing advanced tests such as Radioimmuno assay [RIA] or Enzyme linked immuno sorbent assay [ELISA]. Also possible is a Double Blind Food Challenge Test, in which you will be given food disguised and given to you. This is carried out over a few days.
This is the principle you must follow. You'll have to do a lot of trial and error, but once done, half the battle is won.
- Keep a food diary. Write down all the foods you eat or drink over a period of a week and watch out for symptoms. Next, eliminate one food at a time.
- Ask about hidden ingredients in foods. Example eggs might be one of the contents in chocolates, few types of cereals, salad dressings, noodles etc., or chutneys and sauces could contain peanuts.
- Read food labels and become familiar with technical as well as scientific terms.
- Have anti-histamines handy.
- Carry an allergy card with personal details, types of food allergies, medicines needed in case of an attack and the contact details of the doctor.
A common confusion
Often people are confused between food allergy and food intolerance. Both are different concepts. Food intolerance has nothing to do with the immune system. We are intolerant to a food because our body cannot digest it. It could be due to old age, trauma, stress, accident or some deficiency. One of the most common examples is lactose intolerance, wherein people find it difficult to digest milk or milk products due to lack of the enzyme lactase. Certain other foods that cause intolerance are chocolates, caffeine, monosodium glutamate or a few food colours.
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