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Culprit foods
Cow’s milk
Allergy to cow’s milk is relatively common during the first two years of life. Cow’s milk contains various proteins capable of causing allergy. Also, cow’s milk is introduced into children’s diet at a very early age, when an immature digestion process (which fails to break the proteins into smaller, non-allergenic fractions) and immune system (which fails to distinguish properly between harmless and harmful substances) favour the development of an allergy.
Luckily, most babies allergic to milk outgrow this problem by the age of 4-6 years, mainly due to a maturation of the immune and digestion processes.
In the majority of cases, the signs of allergy appear only after the baby is weaned. It can manifest as digestive problem: vomiting, diarrhoea, abdominal cramping or in the form of atopic eczema.
Treating allergy to cow’s milk consists of replacing it with substitutes such a special hypo-allergenic milk formula. If your child is also allergic to these substitutes (which sometimes happens) many doctors suggest that you should use protein hydrolysates (proteins that have been broken down) which are much less allergenic than whole proteins.
Eggs
Eggs are also introduced into a child’s diet at an early stage and are another frequent cause of food allergy in infancy. Hypersensitivity to egg is often associated with an allergy to cow’s milk but may also occur by itself.
Most egg allergens are found in the egg white. However, egg yolk also contains allergenic proteins. Therefore if your child is allergic to egg you should avoid both.
Certain vaccines are prepared on chicken embryos and therefore people allergic to eggs fear that the vaccine could provoke acute allergic reactions in them. The vaccine can be tested on the skin in children with egg allergy. However, measles, mumps and rubella vaccines (which are prepared on cells derived from chick-embryos) contain no, or very small amounts, of egg allergen. Therefore, testing is not recommended unless the child has experienced severe anaphylactic reactions to egg (which, luckily, are very rare in children). Influenza vaccines contain higher quantities of egg allergens and therefore all children and people with documented allergy to eggs should be tested with the vaccine solution before administration of the vaccine.
Peanuts
Peanuts are the most allergenic of all foods and a frequent cause of allergy not only in children but also in adults.
Also, unlike most foods, peanut allergens are not destroyed by heat but rather become more potent. Therefore, roasted peanuts or crude peanut oil are even more allergenic than raw peanuts.
Peanut allergy is often very severe, indeed it can manifest as anaphylaxis. Also, unlike milk and egg allergy, peanut allergy is life-long in most people.
Fish
Fish allergens are proteins found in the flesh portion of fish. They are often common to different species of fish. However, some people are allergic only to a certain type of fish.
As with peanut allergy, fish allergy is life-long in most people and can manifest as severe anaphylactic attacks.
Fish allergens can be very potent. Sometimes allergic attacks can be triggered by minute traces of allergen such as those found in vapours from cooked fish.
Shellfish
Culprits: crustaceans (crabs, shrimps, prawns, lobsters, etc.), and bivalve molluscs (oysters, mussels, cockles, etc).
Here too, these may be mono-allergies (to only one single species) or crossed-allergies (due to their presence in various species, e.g. shrimps and mussels). There is also cross reactivity with house dust mite allergens in some patients.
Fruits, vegetables and nuts
The principal culprits are apples, pears, stone fruits (cherries, apricots, peaches, etc.) and vegetables such as celery, parsley, tomatoes, etc.
Handling and cutting up kiwi fruit can trigger generalised reactions in some sensitive people
Some of the most severe reactions are to tree nuts such as walnuts, hazelnuts, almonds, and Brazil nuts. Even though peanuts are not part of the same family as tree nuts (they belong to legume or bean family), some 20% of people allergic to peanuts are also allergic to tree nuts. Also people with tree nut allergy can be allergic to peanuts. Therefore, it is advisable that if you are allergic to one type of nut you should avoid nuts altogether.
Boiling the milk doesn’t help!
Milk proteins are resistant to heat and can still be very allergenic even after cooking
Breast-feeding mothers should be careful with their diet
Some breast-fed children show signs of allergy after the first few feedings because mother’s milk may contain small quantities of cow’s milk allergens (if the mother is consuming cow’s milk). However, this is a very rare occurrence. The general rule still stands: Breast is best!
Remember that infants cannot tell you when they are in pain. They cry instead, so if your child is restless and crying repeatedly after a meal containing milk think that there must be a reason behind his crying!
Cooking eggs at high temperatures and for long time may destroy the allergens, making the egg allergen-free. However not all egg allergens are destroyed by heat and therefore some people cannot eat eggs, regardless of the way they are cooked.
Intolerance to milk and eggs decreases as a child grows, so as the child becomes older you may very cautiously try re-introducing foods which previously caused a reaction - but always consult your doctor first!
If you suffer from peanut allergy you must be very diligent in avoiding all foods containing peanuts or peanut products (such as dishes prepared with peanut oil). Remember that oriental restaurants frequently use peanut oil for cooking or in sauces. A quarter of peanut allergic individuals also react severely to lupine flour which is found in pastries, pizzas and some doughs.
Hypersensitivity to fruits and vegetables is often related to an allergy to pollen. For example, 50% of people allergic to birch pollen are also allergic to apples. The allergens in fruit and vegetables are frequently, but not always, thermolabile, i.e. they are destroyed when cooked. This is called the oral allergy syndrome (OAS). In Northern Europe OAS is usually mild, involving itching and swelling of lips and tongue; however in Spain it can be severe and anaphylactic because a different set of molecules is recognised.
Remember that the most effective treatment of food allergy is to avoid eating the allergenic food. With some foods (such as cow’s milk and eggs) allergy may fade in time, so you might be able to safely eat them after a few years of avoidance. With other foods (such as peanuts, fish and shellfish) allergies are for life and you will never be able to eat that food again.
Never try to eat a food that once caused you an allergy without consulting your doctor