Sunday, July 14, 2013

Genetics of Food Allergy and Intolerance

Can genetics explain if you are allergic to some pollens or foods?

White blood cell patterns determined genetically and designated as HLA DQ and DR genes have been identified with an increased risk of pollen, dust, latex, and food allergies. The intriguing part of this story is that there is an advantage to knowing your HLA DR and DQ type when evaluating your risk for pollen allergies and their associated food allergies or cross reactions.

Genetics of Food Reactions and Allergies

As I explain in more detail in my articles on the genetics of gluten sensitivity, we all have proteins on the surface of our cells that are genetically determined. These patterns are easily detectable by testing cells from blood or from the mouth obtained by a Q-tip type swab. Specific patterns have been associated with increased risk for autoimmune conditions, gluten sensitivity and celiac disease.

HLA DQ Genetics and Celiac or Gluten Sensitivity

HLA DQ2 is present in more than 90% of people who have celiac disease while HLADQ8 is present in most of the rest, though not all people with celiac have been found to have DQ2 and/or DQ8.

DQ and DR Genetic Patterns Associated with Food and Pollen Allergies or Sensitivities?

Now it appears certain DQ or DR patterns are associated with food and pollen allergies as well. As the Food Doc, I continue to search the literature for more information about genetic links to food allergy and intolerance. My search has led to me to a couple of interesting articles in the unusual area of oral allergy syndrome (OAS). The relationship between seasonal and perennial nasal allergies and food allergies is certainly well established but not generally known by most doctors or patients. It appears that some of us need to avoid eating certain foods if we have hay fever or allergies, especially during the hay fever season. This problem also appears to be inherited.

Research Documents Genetic Association With Certain Food and Pollen Allergies

Boehncke, et al. from the University of Frankfurt reported in 1998 that certain white blood cell types known HLA class II genotypes or HLA DQ and DR genetic patterns were found more frequently in people with certain pollen associated food allergies. HLA-DQB1*0301 is present in more people with grass pollen allergy. Those with HLA-DRB1*08, an inherited white blood cell protein pattern linked with a grass pollen allergy, have six times the increased risk of peanut allergy. Those who have inherited the HLA-DRB1*12 white blood cell pattern are 13 times higher at risk for carrot allergy.

Tree Pollen Allergy to Birch Tree Pollen Appears to be Worst

Birch pollen associated hazel nut allergy is linked to HLA-DRB1*01, DQA1*0101, and DQB1*0501. Hazel nut, almond, walnut and apple are the most common food allergies associated with birch tree pollen. Allergies to those foods are commonly associated with birch tree pollen in other studies.

Weed Allergies Also Associated With Food Reactions

In 2004, Wang et al. from China published that the inherited white blood cell type DQA1*0302 is found in more people with Artemisia pollen-induced allergic rhinitis, hay fever due to Mugwort or Sagebrush weeds. Mugwort allergy is associated with several food allergies including apple, celery, hazelnut, pistachio, lettuce, almond, peanut, and carrots.

Where to Get Genetic Testing

There are three commercial labs that I am aware of that offer full HLA DQ typing. They are Quest Laboratories, The Laboratory at Bonfils in Denver, and Enterolab. Bonfils runs the Enterolab genetic tests. Enterolab offers the test run on samples of cells obtained from a Q-tip swab of the mouth. The test can be obtained directly from Enterolab without a doctor's order though it is not covered by insurance. It however is very reasonable from a genetic testing standpoint at $149. Bonfils also does the DQ typing on cells obtained from blood samples sent to them from other labs.

The Future of Genetic Testing in Pollen and Food Allergies

In the future such testing should be very helpful in evaluating suspected food allergies, intolerance and pollen allergies. In the meantime those of us interested in this interesting story anxiously await more research findings in this exciting area. Dr. Fine, founder of Enterolab, has previously published the HLA DQ patterns associated with microscopic colitis. He has found that microscopic changes in the colon or large intestine are similar if not identical to what is seen in the small intestine in celiac disease. Several articles now document that a gluten free diet works in many people with microscopic, lymphocytic and collagenous colitis. It also helps many with Crohn's disease and ulcerative colitis.

A finding of intraepithelial lymphocytosis in the distal small intestine (terminal ileum) is associated with an increased incidence of celiac disease in the proximal small intestine. Now, adding to the intrigue, are these articles linking certain inherited white blood cell protein gene patterns to pollen allergy and food allergy cross reactions that are well recognized but rarely pursued clinically. Oral Allergy Syndrome (OAS), also called the "burning mouth syndrome", occurs in many people but frequently goes undiagnosed. Symptoms include burning, painful and/or itching sensation of mouth or throat with or without swelling that occurs almost immediately after eating certain foods. The foods causing these reactions are commonly associated with pollen, latex or dust allergies.

Unusual Association of Pollen Allergies and Mouth Burning or Food Reactions

This unusual association of tree, grass, and weed pollens, latex and house dust mite allergies to food reactions, though well documented in the medical literature, is not commonly recognized by doctors or patients. The OAS literature contains numerous reports of food allergy or intolerance reactions that are associated with specific pollen, dust, mold or latex allergies. One of the best examples is ragweed pollen allergy. It is associated with a higher risk of food allergy or intolerance to only a few foods. These include foods in the gourd family (cucumbers and melons) and bananas. On other the hand, Birch tree pollen allergy is associated with sensitivity to many foods. The list includes those foods in the Rosacea family (apples, pears), tree nut family (hazelnut, almond, walnut), potatoes, and carrots. Reactions include classic allergic reactions such as skin rashes (atopic dermatitis, hives), wheezing (asthma), runny nose (allergic rhinitis), as well as the burning mouth OAS symptoms and other food intolerance symptoms.

If You Suspect Food Allergy, Intolerance or Sensitivity Get Evaluated By an Expert

Individuals who suspect food allergy or intolerance are encouraged to review the food-pollen connection and undergo appropriate evaluations for food allergy, intolerance and sensitivity. Food sensitivity includes gluten sensitivity and cow's milk (casein) protein sensitivity. Food intolerance includes lactose intolerance. Food allergies are separate and distinct from either food sensitivity or food intolerance.

Consider Getting Genetic Testing or Asking Your Doctor to Test You

This new information about the link of white blood cell protein patterns, HLA DQ types, suggests that we should consider having genetic testing done. After an adequate evaluation,

Establish a Baseline Symptom Score and Start a Food Symptom Diet Diary

I encourage everyone to establish a baseline symptom score. A detailed food symptom diary before a trial of elimination diet is also extremely helpful. An elimination diet that excludes major food lectins (dairy, grain, legumes, and nightshades) and any foods from the pollen list that one is allergic is recommended before accepting diagnoses of IBS, fibromyalgia, unexplained neuropathy or headaches, and chronic fatigue syndrome. Any symptoms not readily explained or improved with other diagnoses and treatment should be considered to be possibly due to a food reaction until proven otherwise.

Selected Bibliography

Boehncke, et al. Clin Exp Allergy. 1998 Apr;28 (4):434-41.

Fine KD et al. Am J Gastroenterol. 2000 Aug;95(8):1974-82.

Wang et al. Otolaryngol Head Neck Surg Feb; 130(2): 192-197.

No comments:

Post a Comment