I would like to share some background on some of the more rare and fascinating food allergies which exist, some of which have presented to me for advice at the nutrition clinic.
Pollen Cross- Reactions
A patient once reported itching in her mouth and throat when she ate several fruits and vegetables, Raw fruits and vegetables caused much more discomfort than cooked, so she stopped eating the ones she thought were causing this reaction. Interestingly, individuals with an allergy to birch tree pollen can have symptoms that mimic food allergies when they eat raw fruits and vegetables. The pollen is present in or on the skin of the fruits and vegetables. There is either cross-contaminated with birch tree pollen or the food may contain proteins that are similar in structure to birch tree pollen that can cause sensitive individuals to experience intense itching in the mouth and throat. In the case of the above patient, it is known as oral allergy syndrome (OAS) or pollen food syndrome.
Cross-reactivity, between pollen and apples for example describes an event where antibodies are released by the immune system in response to a protein that’s similar to the protein responsible for the true pollen allergy. Proteins that are similar to one another can confuse the immune system, causing it to react to the wrong substance. Typically, symptoms are contained in the mouth and quickly resolve on their own once the individual stops eating the offending food. Severe reactions are possible, particularly if throat swelling is involved, since this can cause breathing difficulty. Those who believe they have OAS should be evaluated by a medical doctor or consultant who specialised in allergies to out-rule a true food allergy. It’s common for many individuals who experience OAS to believe they are allergic to fruits and vegetables, but in many instances they should not have to avoid them. It is often possible to consume the particular fruit or veg if it is washed very well, remove the outer skin where possible and experiment with cooked vs. raw foods.
Spices not only help make foods taste better but also add various health benefits. However, for a small percentage of people, spices can cause dangerous allergic reactions if ingested. Spice allergy symptoms are similar to hay fever, but they can be much more severe. Coriander is in the family of spices that includes caraway, fennel, and celery—all of which have been implicated in allergic reactions in recent years, and they’re not alone. Cinnamon, saffron, and mustard also have been noted for causing reactions. In Spain, an interesting study found that mustard appears to be related to cross-reactivity to birch tree pollen but also may be associated with mugwort and ragweed pollen allergy. Eating out can be difficult for people with food allergies and the patience and carefulness of restaurant staff is well appreciated amongst those suffering from an allergy.
What does latex have to do with food allergies? As much as 50% of those with an allergy to natural rubber latex also will have cross-reactivity to certain foods, according to Dr. Isabel Skypala, Dietitian in the UK. Individuals with latex allergy have an increased risk of developing food allergy reactions, most commonly to avocados, bananas and kiwis, but may also be sensitive to apples, carrots, celery, melons, papaya, potatoes and tomatoes. Many proteins are found in natural rubber latex, so food proteins that are structurally similar to one or more of these proteins have the potential to cause cross-reactivity. People with sensitivity to these foods based on a latex allergy usually experience symptoms within minutes of ingestion. Reactions to natural rubber latex allergy can be life threatening; however, food allergy related to latex allergy usually is less severe.
Food allergy testing may be available through GP referral. Food intolerance testing i.e. IgG testing is not recommended by the Irish Food Allergy & Intolerance Network (a relatively new board established in Ireland by Dietitians and Medical consultants who specialise in allergies). The European Academy of Allergy & Clinical Immunology also advocate against IgG intolerance testing.
Other non-validated testing methods include;cytotoxic food testing, kinesiology, Vega testing, electrodermal testing, pulse testing and hair analysis. These tests have not been scientifically proven effective and may lead to unnecessary, costly and in some cases involve dangerous avoidance strategies.