A food allergy is an abnormal response to a food triggered by our body's immune system. Symptoms can occur when coming in contact with even a tiny amount of the food. As some of the symptoms of intolerance and allergy are the same, it is quite common that many people consider themselves 'allergic' to certain foods, while in reality they are 'intolerant.' Often people experience an itch in the mouth and throat after eating raw or uncooked fruits or vegetables, which may be indicate oral allergy syndrome, but not to the food itself. Eight types of food account for about 90 percent of all reactions allergic reactions — eggs, milk, peanuts, tree nuts, fish, shellfish, wheat, and soy.

Common symptoms may include — vomiting; diarrhoea or abdominal cramps and pain; itching or swelling in the mouth; hives or eczema; drop in blood pressure; shortness of breath; wheezing; tight, hoarse throat; trouble in swallowing; swelling of the tongue, affecting the ability to talk or breathe; weak pulse; pale or blue colouring of skin; and dizziness. There is also a chance of having anaphylaxis, a potentially life-threatening reaction that can impair breathing and send the body into shock.

Most  food-related  symptoms  occur within  two  to  six  hours  of  ingestion  but they  can  start  within  minutes  after  consumption  of  the  food.  Delayed  reactions are  most  typically  seen  in  children  who  develop  eczema  and  severe  gastrointestinal  reactions  that  generally  occur  after consuming  milk,  soy,  and  certain  grains.

While allergies tend to run in families, it is impossible to predict whether a child will inherit a parent's food allergy or whether siblings will have a similar condition. 

Food allergy can be diagnosed by laboratory tests, but very few are available in our country. Therefore, a person needs to identify the food s/he is allergic to depending on the symptoms. For infants and children, parents should be careful in identifying the symptoms.

Once an allergy is diagnosed, the most effective treatment is to avoid the food. People allergic to a specific food may also potentially have a reaction to related foods. Those allergic to shrimp may react to crab and lobster as well. Allergies to milk, eggs, wheat and soy may disappear over time, while allergies to peanuts, tree nuts, fish and shellfish tend to last. 

It is advised that mothers breast-feed their children for as long as possible to prevent food allergies in infants.