Food allergies have been gradually increasing in incidence across the world. They can be a drag for kids, depriving them of some of their favourite foods like cakes or nutty chocolates, besides causing serious nutritional deficiencies. They can be a source of embarrassment and anxiety for adults, especially those with severe and life-threatening allergies.
It is also fairly common to mistake food intolerance with true food allergy. In case of a bad reaction, time is of the essence, and learning about food allergy coping techniques can save a life.
Most of us have had an unpleasant reaction to something we ate at some point in our lives; either in the form of an itchy throat, bloating or diarrhoea. It makes us wonder if we are allergic to that food. But in reality, only 3% of all adults and 5-6% of all children have a clinically proven true allergy to one or more food items. The most common culprits have been referred to as “the big eight”. These include milk, eggs (the white of the eggs more than the yolk), peanuts, tree nuts (almonds, cashew, coconut, hazelnut, walnut etc.), seafood, shellfish, soy and wheat. While some children can outgrow their food allergies, in adults it tends to be lifelong. Food allergies can show cross reactions as well, which add to the list of foods to avoid. For instance, if you have a severe allergy to crab, you could be allergic to shrimp as well. Those with severe peanut allergy can cross react with other nuts as well. If you are allergic to cow’s milk, you could be allergic to beef as well!
So what exactly is a food allergy and how did I get it? Food allergy is an abnormal response of the immune system to the protein present in certain food items. Certain protein or protein fragments are resistant to the acids and enzymes of digestion. Our immune system mistakes these proteins for ‘foreign invaders’ and responds by releasing certain antibodies (called IgE) and chemicals (called histamine) into the blood stream, which are responsible for the typical symptoms of food allergy. These antibodies keep building up in our system with each subsequent “attack”, which is why food allergies tend to become more severe with repeated exposure to the offending food item. Food allergies can be inherited in a hereditary fashion. And they tend to be more common in individuals who already suffer from other allergic conditions like eczema, asthma and allergic bronchitis. Allergies can begin as early as one’s infancy. Exclusive breast-feeding for the first 6 months of life can minimize and prevent the risk of food allergies in infancy, though there is no evidence to prove that it can prevent the onset of food allergies later in life.
How does a food allergy manifest itself? The symptoms can be noted within minutes to up to an hour of eating the culprit protein. The severity is often unpredictable and multiple organs can be affected. The symptoms can vary from person to person but they include itching around the lips, tongue and throat, itchy hives (red welts) and eczema (red scaly areas) on the skin, a runny nose, nausea, vomiting, stomach cramps and diarrhoea. These symptoms can last for up to 2 hours.
Severe allergic reactions can manifest in the form of a life-threatening condition called “anaphylaxis”. The symptoms of anaphylaxis include swollen lips or tongue, swelling around the eyes and genitals, hoarseness of voice, and drop in blood pressure (leading to light-headedness and fainting).
Anaphylaxis can quickly lead to choking sensation with difficulty in breathing and swallowing, which can prove fatal within minutes if the reaction is not reversed quickly with medication. Individuals with severe allergies are at special risk as even touching a few crumbs of nut can trigger an anaphylactic shock! In fact, the severity of food allergies is directly proportional to the amount of food allergen ingested. If an infant is allergic to wheat, the mother must avoid wheat in her diet as well, as the wheat protein can be passed on to the child through breast milk.
Food allergies can have rare and interesting variants as well. For instance, if your mouth suddenly begins to itch after eating certain fruits like apple or melon, you may in fact be allergic to the pollen on these fruit rather than the food itself. Such allergies only occur when you eat the food in its raw state during the pollination season, and do not occur when the food is cooked. Certain food allergies only manifest when the body gets heated (for instance, by exercise) within an hour of having a meal.
Certain illnesses can mimic food allergies. Lactose intolerance is one famous example. It is caused by the deficiency of enzyme Lactase in the gut, which is needed to digest ‘lactose’, a complex sugar present in milk. It can lead to symptoms like bloating, flatulence and diarrhoea, but this is not an allergic condition, and the symptoms will not improve with anti-allergic medication. Gluten intolerance is also mistaken for an allergy as patients develop diarrhoea, malabsorption and skin rashes on ingestion of wheat, oat, rye and barley which contain a protein called gluten.
Certain food additives like food colours, preservatives and MSG (monosodium glutamate) can also cause skin rashes and heartburn but this is not a food allergy either. Food poisoning is caused by bacterial contamination. Peptic ulcers and irritable bowel syndrome is caused by infections and stress, and although they share some of the same symptoms, these are not allergic conditions either.
How are food allergies diagnosed and confirmed? Careful history taking is key. In most cases symptoms may appear within minutes of exposure, so most patients are in fact well aware of their allergens. In those who have not been able to figure it out, an elimination diet along with maintenance of a food dairy can help. Here one particular food item like milk (and all dairy products) is completely eliminated from the diet for a few days. If your symptoms improve, then reintroduce that food item into your diet. If your symptoms recur soon after the reintroduction, then this clinches your diagnosis. If your symptoms do not improve with the elimination of just one food item, then eliminate other food items a few days at a time till your symptoms disappear, then reintroduce them one at a time till your allergies recur. This is a time consuming and imprecise process which requires care and patience, but this is a reliable, inexpensive and non-invasive test. However this technique is not useful if your reactions have been infrequent or too severe.
The other tests include skin prick testing or a blood test. Skin testing is the most popular and reliable test employed by allergists and some dermatologists, but the success depends on the expertise of the person interpreting the test. Here a small amount of the allergen in liquid form is put on your skin and a needle is pricked through it very superficially, to push the allergen into the dermis of your skin. 30 or more different allergens can be tested this way on a single day by testing on the skin of your back. The allergens which cause a tiny swelling at the site of the prick, are said to be the offending allergen. On the flip side, false positive reactions are very common with this type of testing.
Skin prick tests cannot be done in children who tend to be uncooperative around needles. They cannot be done in pregnant women, in patients with extensive eczema of the skin, or in patients who’ve had anaphylactic reactions. A blood test called RAST (radio-allergosorbent test) can be done for such patients and hundreds of allergens can be screened from a single sample of blood. However the results take a long time, the test is very expensive and offered only at select facilities, and may give false negative results.
Food oral challenge test is considered the gold standard investigation. Here various food allergens are given in opaque capsules form such that both doctor and patient do not know which food item is being tested (the capsules are prepared by a nurse). This is a very risky test and must only be performed in a hospital setting where emergency care can be administered in case of an anaphylaxis. This test is mostly used to differentiate true food allergies from food intolerance and other medical conditions.
Food allergies cannot be cured and are often life-long. However, they can be successfully managed by identifying the allergen and avoiding it scrupulously. This may involve carefully going through the ingredient list of every food item to ensure that it does not contain milk, soy, eggs or nuts. For instance, food that contain tree nuts include pesto, nutella, baklava, muesli, granola bars, flavored coffee and pralines. Doctors often prescribe alternatives in order to prevent nutritional deficiencies. Cow’s milk can be replaced by soy milk or coconut milk. Use sunflower seed butter instead of peanut butter. Use flaxseed, sunflower seed or pine seed as a substitute for nuts, use tofu in place of soy cheese; and use rice, almond, maize, millet or tapioca flour in place of wheat.
Antihistamines like Allegra or Alerid can help alleviate the bothersome symptoms of food allergies. Oral steroids are prescribed in the resistant and recalcitrant cases. Anaphylaxis is a medical emergency. Time is of essence, and often patients find themselves alone at home, or cannot reach the emergency room in time. Each subsequent reaction is more severe than the last one, so it is a good idea to carry a preloaded syringe of single dose adrenaline in a pen form on your person in case of emergency. These pens are available under the trade name Epipen or Twinject (available by prescription only) and you can inject yourself painlessly. Consult your allergist or immunologist for more information on Epipen and Oral Immunotherapy. Some people wear stainless steel medical emergency bracelets announcing their allergies or how to administer the Epipen.
My parting shot? Food allergies are becoming increasingly common around the world, perhaps due to improved awareness, or as a price of modernization, not discounting food intolerances as well. However death due to food allergy is becoming rarer due to improved awareness and compulsory food labelling enforced in many countries. When it comes to coping with food allergies, knowledge is power and public health awareness is of paramount importance. Help your physician by noting down your symptoms, every item of your last meal (including candy wrappers etc.), time taken between ingestion to appearance of symptoms, amount of food ingested, whether some of your food was raw or semi-cooked (egg whites, crab etc.), frequency of episodes and co-existing allergies. If you have a child with food allergies, then educate their care-takers (grandparents, nannies and/or teachers) on dietary restrictions, special precautions and emergency care. Most importantly, never ever try to do any allergy testing at home!
