Food allergy is common in infant and young children. It can be frustrating for parents - colicky infants, vomiting, constipation and not tolerating formula or sometimes even breast milk. And for the child, the impact is even more so - failure to thrive is common, which may lead to developmental delay as poor nutrient intake impairs achievement of developmental milestones. Thus, it is important for parents and pediatrician to diagnose food allergy in a timely manner to avoid long-term detrimental outcomes. The good news is most of these allergies in young children will resolve on its own by 4-5 years of age.
Hidden food allergy or intolerances are also common and difficult to identify. Our common perception of food allergy is someone who is allergic to seafood, and ate something with shrimp, and within minutes reacted with full body hives, facial swelling, itching mouth and throat, etc.
However, these are not what we're seeing in children with hidden allergies or intolerances. Reactions to food intolerance are delayed and more subtle. Therefore, they are frequently ignored or dismissed. Food intolerance and food allergy shares many similar signs and symptoms. However, they are very different physiologically.
WHAT IS THE DIFFERENCE BETWEEN FOOD ALLERGY AND FOOD INTOLERANCE?
Food allergy triggers an immediate immune response, usually involving the immunoglobulin E (IgE). IgE-mediated response activates a cascade of systemic reactions, involving multiple organ systems. That is why this is the more severe form food intolerance. Fatal peanut allergy falls into this category. Usually a tiny amount of the offending food can cause an immediate and severe reaction, and may sometimes lead to anaphylactic shock, which is life-threatening emergency.
An anaphylaxis is characterized by systemic responses, such as difficulty breathing due to swelling of airway, hives along with itching, flushed or pale skin, weak and rapid pulse, dangerously low blood pressure, nausea/vomiting or diarrhea, dizziness or fainting.
An anaphylactic event requires emergent medical treatment, and delay of treatment may result in death. People with severe food allergies are usually prescribed and "epi" epinephrine pen that they carry around in case they consume or come in contact with their allergen by accident.
Food intolerance, on the other hand, does not involve the immune system, and reaction also comes on a lot slower - usually after two hours of ingestion of food, and sometimes up to 48 hours with more subtle presentation. Unlike food allergy, an individual usually is able to tolerate a small amount of the offending foods without much adverse effect.
Symptoms of food intolerance are generally less serious, less obvious and appear very subtly and slowly. That's why the trouble food is seldom identified. Some common signs and symptoms include nausea, vomiting, abdominal cramps, constipation, diarrhea, asthma, eczema (atopic dermatitis), etc. Food intolerances may also result in behavioral symptoms frequently seen in ADHD and autism.
Unlike food allergy, food intolerances are not detected by RAST test or skin prick tests, as both these test for IgE circulating in the blood. Reactions in food intolerance are not IgE-mediated. It may be the result of activation of IgG antibodies or other causes.
Once the offending food is identified, it should be avoided completely, especially the reaction is an IgE-mediated reaction. Food allergies are common in the first years of life. With every repeated exposure to the offending food, the immune system becomes better in attacking that allergen, which means the response will become more and more intense with each repeated exposure. Children usually outgrow their allergies by 4 or 5 years of age. However, repeat exposure may prevent or delay the time to outgrow the allergy.