Food allergy is a reaction towards certain food component. It occurs when the cells of the immune system recognize a substance in food as harmful and try to destroy it. The substance which triggers an allergic reaction is called an allergen. The most common allergen in foods is proteins. Food allergies can develop at any age.
While some childhood allergies disappear later in life, a few may last forever. According to experts, children who outgrow one type of food allergy may develop a more severe and persistent type of allergy to the same food. High vitamin D levels in pregnancy could trigger a food allergy in the baby, say researchers. Including solid food besides breast milk in a baby’s diet after the 17th week of birth helps development of a stronger immune system to fight food allergies.
You may think that any negative reaction to food is called as allergy. But, that’s not true. Your body can have several negative reactions to food, but all of them need not be allergic reactions.
Food allergies are reactions towards certain food components that involve the immune system. They occur when the cells of the immune system recognize a substance in food as harmful and try to destroy it. These substances which trigger an allergic reaction in the body are called allergens and the most common allergens in foods are proteins.
Is food allergy and food intolerance the same?
People often get confused between food allergy and food intolerance. Food intolerance is when your body is unable to properly digest a certain foods because of an enzyme deficiency (eg: Lactose intolerance where people are intolerant to milk and milk products). Food allergies, on the other hand, have nothing to do with enzymes. They are caused due to an immunological reaction.
The symptoms of food intolerance do not develop instantly as in case of food allergy and may not be life-threatening. Read more about causes, symptoms, diagnosis and treatment of anaphylaxis.
The symptoms observed are dependent on the type of food allergy.
Wheat and corn allergy
On eating anything that contains wheat and corn, if you notice the below symptoms you could be suffering from the allergy.
- Indigestion, flatulence, stomach ache and diarrhoea
- Hyperacidity and stomach ulcers
- Hyperactivity or aggressive behaviour
- Fatigue and depression
- Muscle pain and cramps
Gluten allergy can cause serious allergic reactions leading to complications like chest pain and tightness, difficulty in breathing and swallowing, swelling of throat, pale skin and very low BP.
Allergy due to milk and milk products
These allergies are common in children and adults who consume cow milk and milk products like ice-cream, lassi, buttermilk, cheese and yoghurt. In India, milk allergy is commonly found in metropolitan cities like Delhi, Bangalore, Madras and Mumbai where the use of milk powder, imported from Europe to provide reconstituted milk, and tetra pack milk or pooled milk is increasing.
According to 1990 estimates, milk allergy was found in less than 5% of Indian population. But as of 2013, more than 50% of people residing in these cities now suffer allergies and health problems caused by milk and milk products.
There are more than 25 different components in milk which have been identified by researchers as potential food allergens. The protein that usually triggers an immunological reaction in milk is S1-caesin. Deterioration of milk quality is also one of the reasons why milk allergy is becoming common in India. Contamination of milk due to widespread use of chemical pesticides on cow feed has increased the chances of allergic reactions to milk.
Common symptoms include wheezing, vomiting or development of an evident red, itchy rash on skin called as hives. Other symptoms which may take a while to fully develop include:
- Diarrhoea and stomach cramps
- Nose irritation and runny nose
- Watery eyes
- Skin rash around the mouth
- In infants, colic is commonly seen
Children and adults with milk allergy rarely develop complications. But they more likely to develop allergies to other foods such as peanuts or eggs which can lead to complications.
Egg allergy: These allergies are common in children and adults who consume eggs in any form and egg products such as cakes, pastries, baked foods, mayonnaise, pasta, soups and wine, which contain eggs. Egg allergies are most common in infants between 6 and 15 months of age. It is believed that egg whites cause more allergy than the yolks. In rare cases, people might be allergic to both.
How is it recognized?
On eating egg or products containing eggs, if you notice the following symptoms you might be suffering from allergy to eggs.
- Red bumpy rashes on the skin soon after eating eggs.
- Vomiting, nausea
- Stomach cramps or diarrhoea.
- Asthma with coughing and wheezing.
- Respiratory symptoms include runny nose and sneezing.
- Watery and itchy eyes
Why do you need to take it more seriously?
Egg allergy can lead to serious allergic reactions (anaphylaxis). Symptoms such as severe stomach pain and cramps, increased pulse rate, dizziness or loss of consciousness can indicate a medical emergency.
Allergy due to peanuts and other tree nuts such as walnuts, almonds and cashewnuts
Allergies are common in children and adults who consume plain roasted peanuts and products containing peanuts. About 33% of individuals who have peanut allergy may also show allergic reaction to other tree nuts.
According to a report published in the Journal of the Indian Medical Association, peanuts are the most common food allergen in India. Peanut allergy is seen in both adults and children. It is observed that about 9% percent of children suffering tree nut allergy and 20% of children having peanut allergy eventually outgrow their allergy as adults.
Researchers believe that exposing peanuts to high temperature while roasting alters their protein structure which increases the likelihood of allergic reaction. Chances of peanut allergy increase in people having other forms of allergy such as asthma, eczema and hay fever.
How is it recognized?
Common symptoms of peanut allergy include:
- Skin reactions, such as hives, reddening or swelling of skin
- Itchy throat and mouth
- Nausea and vomiting
- Diarrhoea, stomach cramps
- Tightening of throat
- Shortness of breath
- Runny nose.
Why do you need to take it more seriously?
Peanut allergy is the most common cause of food-induced serious allergic reaction (anaphylaxis) leading to a life-threatening condition. Complications include:
- Constriction of airways
- Breathing difficulty due to swelling of throat
- A sudden drop in blood pressure
- Increased pulse rate
- Loss of consciousness
Many people think that food allergy does not require medical help if they avoid eating those foods. By simply avoiding foods suspecting that you might be allergic to them may deprive you of essential nutrients and could be also be dangerous if you are allergic to some other foods. As mentioned earlier, every negative reaction to food might not be an allergic reaction therefore a diagnostic test must be performed to confirm an allergic reaction.
In a scratch-the-skin test, a dilute suspension of the food suspected to cause an allergy is placed on the surface of skin on forearm or back. The skin then is scratched with a needle to observe for immediate changes such as swelling or redness. A positive skin test confirms a local allergic reaction to the food.
In certain situations, such as extensive eczema, skin tests cannot be performed as it may lead to dangerous consequences. In such cases, the doctor may recommend blood tests such as the RAST (Radioallergosorbent assay) and the ELISA (Enzyme-linked immunosorbent assay).
Both these tests detect the presence of food-specific IgE antibodies in the blood of patients. They are expensive and the results are not readily available.
Elimination of foods from the diet
Sometimes, the doctor may suggest you to eliminate certain foods from the diet for a few weeks to check whether the symptoms subside. This method is usually combined with a skin or blood test. In some instances, the doctor may ask you to gradually reintroduce small quantities of those foods to your diet. If the symptoms recur, then you are certainly allergic to that food.
An oral challenge test is usually done when eliminating suspected food from the diet does not give conclusive results. In this test, foods suspected to induce allergy along with other foods are given to the patient in the form of capsules. Both the patient and the doctor are unaware of which capsules contain the suspected allergens. The doctor observes whether an allergic reaction has occurred. Oral food challenge confirms a food allergy.