Food allergy occurs when a food triggers an immune system mediated reaction. This reaction involves the antibody IgE (immunoglobulin E), which causes the immune system to release histamine, leading to most of the symptoms of a food allergy.
In children, the most common food allergies occur from cow's milk, hen's eggs, peanuts, tree nuts, soybeans and wheat. In adults, nuts including Brazil nuts, almonds, hazelnuts, peanuts and walnuts are common allergens. Seafood such as fish, mussels, crab, prawn, shrimp and squid may also cause allergic reactions.
In children, the foods most likely to cause anaphylactic reactions are peanuts, tree nuts, other legumes, eggs, fish, shellfish, and milk. In adults, the foods most likely to cause anaphylaxis are peanuts, tree nuts, shellfish, and fish. There are a few foods with an undeserved reputation for causing allergic reactions. Strawberries, citrus fruits, and tomatoes very rarely trigger an allergic reaction, and nobody is allergic to sugar.
Magnitude of this problem in children
In 2007 in the US, around 3 million children under 18 had food allergies as per the figures from the Centers for Disease Control and Prevention (CDC). Allergies have become commoner than earlier times and improvements in diagnosis partly explain this change. Also, the current trend of extreme cleanliness is considered responsible for the removal of immune system benefits from early exposure to bacteria.
It has been put forth that a lack of exposure to specific foods in infancy may result in allergies to those foods later on. The irony of the situation is that once an allergy develops, the only option is to manage the symptoms, and preventing food allergies from developing in the first place is still inescapable.
The American Academy of Allergy, Asthma and Immunology now proposes the addition of vegetables, rice, meat, and fruit to a child's diet between 6 months and one year for a quicker identification of problem foods. Thereafter, a child should try milk, wheat, corn, citrus fruit, and soy and at age 2, eggs and at 3, fish and peanuts. Also, researchers suggest that children with allergic parents should be considered at high risk but breastfeeding for the baby's first four to six months of life is said to provide some protection.
Symptoms of food allergy
Symptoms are usually rapid and appear almost immediately after eating. These include skin rashes such as urticaria, hives, itchy skin; itchy nose and eyes with runny nose, wheezing, coughing and difficulty breathing; and swelling and itching around the lips, eyelids and mouth. GI symptoms include nausea, abdominal cramps, bloating, vomiting and diarrhea.
Diagnosis of food allergy
Many food allergy symptoms can be caused by conditions other than allergy and it may take some time to identify the problem food and confirm that you have an allergy. If an allergy seems likely, then your doctor may refer you for allergy testing at a specialist allergy clinic.
Elimination and challenge diets
The doctor may ask you to eliminate the suspected allergy food from your diet and replace it with another food. If improvement in symptoms is observed, a diagnosis can usually be made. To confirm this diagnosis, the doctor may then ask you to re-introduce the food back into your diet. In case you developed severe allergy symptoms with the problem food in the past, then it becomes imperative to re-introduce the food item under medical supervision in hospital. It is all the more important for children because by cutting out certain food groups, they are likely to develop malnutrition.
Skin prick tests
This test is done by putting an extract of the suspect food (preferably fresh food extract) on a small patch of skin, usually on your forearm or back, after making a very small, fine scratch. If redness and swelling develops around the scratch, the test is said to be positive for that food. But there is a possibility of developing false positive results with this test. Thus the test isn't always completely reliable, so it's usually used in combination with other tests. Also, a risk is associated with the test if you experienced severe allergic reactions in the past thus the test should always be carried out in hospital.
The RAST (radioallergosorbent) test on a blood sample measures levels of food-specific antibodies in the blood. This test can produce false positive results (as in skin prick tests), or false negative results (when body produces antibodies but they fail to circulate in the blood).
What should be done in case a child is allergic to a certain food?
The only way to treat food allergies is to avoid the offending foods. This isn't always as simple as it sounds. If your child is allergic to cow's milk, it is a must to check food labels for terms like casein, whey, lactalbumin etc. Progress towards thorough labeling of food allergens has led to better management of allergies. But can always call the manufacturer if you have any doubts regarding the contents of a product. You need to be extra vigilant in case your child is allergic to peanuts or tree nuts. These allergies tend to be the most severe as nuts are ingredients in a large variety of food items, especially in cookies and desserts.
It is important to teach your child to watch out for nuts in any form, and to explain him the risks associated with trading lunches at school. Simply washing hands with soap and water can remove peanut allergens. It is important to remove problem foods from surfaces of kitchens at home, as well as at daycare facilities and schools. These easy-to-do measures will help prevent peanut allergy reactions in children. Also, it is wise to make sure that all their carers and teachers are aware of your child’s allergy, and have the required knowledge and ability to react correctly in an emergency.
It is advised to keep potential food allergy triggers out of your child's diet during very young age, especially if these allergies have been observed in family members. It is believed that if a child isn't exposed to a potential trigger while he is at a high risk, he may never develop allergy to the food.
An antihistamine can be prescribed to ease the symptoms of a mild reaction, and a doctor can help him learn to manage conditions like asthma or eczema with the use of bronchodilators. A kit containing the drug epinephrine (adrenaline) and an easy-to-use needle is given by the doctor in cases of severe allergies. A quick shot of epinephrine can save the child's life if he goes into anaphylactic shock.
Does a child’s allergy go away?
Children usually outgrow the allergies to eggs, milk, wheat, or soy, especially if they completely avoid them (elimination diet) for two or three years. More than 85% of children outgrow allergies to milk, but fewer outgrow allergies to peanuts (about 20%), tree nuts or seafood. With supervision of your doctor, you can usually bring the problem food back into your child's life. But be sure to start gradually; for example if your child was allergic to eggs, it is ideal to offer him a few baked goods with eggs in the mix, and not an omelet.