This week (May 10-16) is National Food Allergy Awareness Week. Food allergies and intolerance are hot topics and something I work with frequently. Food allergies seem to becoming more prevalent and the exact reasoning behind that is not known. According to the CDC food allergies in children rose 18% from 1997 to 2007. Adult onset allergies are also on the rise with at least 15% of people developing allergies after age 18. There are a lot of theories and hypotheses on why allergies develop that are currently being researched. There is still a lot of unknowns, but there is evidence supported recommendations for reducing overall risk of allergies in children.
What is a Food Allergy?
Food allergy is an abnormal response to a food, triggered by the body’s immune system. The “classic food allergy” reaction is an IgE reaction in which the body produces a specific type of antibody, called immunoglobulin E (IgE). The IgE antibodies bind to the food triggers and create an immune response.
The most common allergenic foods in infants and children are egg, milk, peanut, tree nuts such as walnuts, soy (primarily in infants) and wheat. In adults, the most common foods that cause allergic reactions are the shellfish such as shrimp, crayfish, lobster, and crab, peanuts, tree nuts and fish such as salmon.
An allergic reaction to food can present as a number of different symptoms including:
- Itching in your mouth or swelling
- GI symptoms, such as vomiting, diarrhea, or abdominal cramps and pain
- Hives or eczema
- Tightening of the throat and trouble breathing
- Drop in blood pressure
Oral allergy syndrome (OAS) is an allergy to certain raw fruits, vegetables, and/or nuts. OAS is mainly associated with birch and ragweed pollen allergies, so people suffering from hay fever due to those allergies are susceptible to OAS. Symptoms include an itchy, tingling sensation in the mouth, lips, and throat when the foods are eaten. More severe reaction can include swelling of the lips, tongue, and throat; watery, itchy eyes; runny nose; and sneezing. Cooking or processing breaks down the proteins in the fruits and vegetables that cause OAS, so most individuals are eat cooked or processed versions of the fruits and vegetables.
Oral Allergy: Plants, Foods That Cross-React
Exercise-induced food allergy is a type of reaction that is triggered by exercise after consuming the food. Exercise raises body temperature and triggers itching and light-headedness, hives may appear, and even anaphylaxis may develop. Crustacean shellfish, alcohol, tomatoes, cheese, and celery are common causes of exercise-induced food allergy reactions.
Food Protein-Induced Enterocolitis Syndrome (FPIES), also known as a delayed food allergy, is a severe condition in which an allergic reaction (typically vomiting and diarrhea) occurs hours after eating the trigger allergen. FPIES reactions are thought to involve cells of the immune system rather than IgE antibodies.
There is also food allergy associated chronic disease called Eosinophilic esophagitis (EoE). EoE is characterized by inflammation and accumulation of a specific type of immune cell, called an eosinophil, in the esophagus. Symptoms of EoE include nausea, vomiting, and abdominal pain after eating. A person may also have symptoms that resemble acid reflux from the stomach.
Is a Food Intolerance the same thing?
Food allergies and intolerance are not the same. A food allergy typically comes on suddenly, can be triggered by a small amount of food, happens every time you eat that food and can be deadly.
Food intolerance, on the other hand, usually comes on gradually, may not happen every time you eat the food or may depend on the amount eaten, and is not life threatening.
Lactose intolerance for example is a lack of the lactase enzyme that breaks down lactose, the sugar found in milk and milk products. Lactose intolerance is not a immune reaction and is not life threatening. People may have varying degrees of lactose intolerance and may be able to tolerate small amounts. Symptoms are usually GI problems such as gas, bloating, diarrhea or constipation. Gluten and other food intolerance are similar.
Other types of food intolerance include reactions to food additives like MSG and sulfites. Symptoms may include flushing, sensations of warmth, headache, chest discomfort, and breathing problems in people with asthma.
Possible Causes of Food Allergies
In Children
One possible cause is known as the hygiene hypothesis – the idea that lack of early childhood exposure to germs and 
infections depresses the immune system and makes children more susceptible to allergies.
Another possible cause is vitamin D deficiency. Studies have shown that as food allergy prevalence has increased, so has vitamin D deficiency. According to an article by the American Academy of Allergy, Asthma, and Immunology, areas further away from the equator have been shown to have higher rates of childhood food allergy-related hospital admissions, epinephrine autoinjector prescriptions, and peanut allergy (up to six times the risk) than areas closer to the equator. Season of birth (being born in autumn or winter when there is less UVR exposure) has also been associated with higher risk of anaphylaxis and food allergy.
A third, common theory, is that food allergy risk is affected by the gut microbiome, or the makeup of our intestinal bacteria. The diet of those in developed countries paired with the increased use the antibiotics and incidence of C-Sections is thought to have a big impact on the microbes in the gut. A study found that mice given antibiotics early in life were much more susceptible to peanut sensitization, the equivalent of the human peanut allergy. Researchers found that introducing certain healthy, naturally occurring bacteria reduced the sensitization. The hope is to research this in humans to see if supplementing/replacing beneficial gut bacteria would be an effective treatment for food allergies.
In Adults
Adult onset food allergies seem to be triggered by changes in the immune system. Whether it is the hormonal changes from pregnancy or menopause, or aging or co-morbid illnesses suppression of the immune system seems to increase risk for developing food allergies.
Risks for Food Allergies
- 1st degree relative, if a parent has a food allergy, then the child is at increased risk
- Eczema – 25% of children with food allergies have eczema
- Other allergies, such as seasonal, environmental, or chemical
Reducing Food Allergy Risk in Children
A lot of research has been done on the effect of exposure to allergenic foods during pregnancy, breastfeeding and when introducing solid foods. During pregnancy and while breastfeeding, the mother should eat a balanced diet including all potentially allergenic foods (unless the mother herself has an allergy). There is no conclusive evidence that avoiding potentially allergenic foods will prevent a child from developing food allergies.
Babies should be breastfed exclusively for 4-6 months. A 2013 study, found that introducing solid foods before 17 weeks actually increased risk for developing food allergies. It is recommended that babies continue to breastfeed while introducing solids to receive the immunological factors in breast milk and educate their immune systems to further reduce risk. New foods should be introduced one at a time and parents should wait 2-3 days before trying another food. Parents should watch for diarrhea, rash, or vomiting as signs of a food allergy. Several studies have actually shown an increased risk of developing allergies when there is a delay in introduction of foods past 6 months.
Overall, there is still much research to be done to pinpoint why the prevalence of allergies has risen and what we can do to prevent or treat food allergies.
For more information on food allergies:
National Institute of Allergy and Infectious Diseases
American Academy of Allergy, Asthma & Immunology
All in Moderation 