Ask the Allergists

With Dr. Susan Waserman and Dr. Wade Watson

Q My son is allergic to peanuts, tree nuts and all seeds. I’m curious about the seed allergies: why is sesame viewed as a major allergen and declared in the ingredients of foods while sunflower seeds and oil are not? Also, since seeds are an issue, should we be worrying about mustard and mustard seed?

Dr. Watson: I have reviewed the Canadian Food Inspection Agency website with regard to food labeling. Currently, the 11 priority food allergens identified by CFIA were declared as they account for more than 90 per cent of severe adverse reactions related to food. They include peanuts, nuts, sesame seed, milk, egg, fish, shellfish, soy, wheat, sulphites and mustard.
My interpretation would be that sunflower seeds were not part of this group because they were responsible for fewer reactions. For your son, I realize that this is not relevant. Mustard is, indeed, a seed. There have been a number of reviews of cross-reactivity in food allergy. Although there are a number of seed storage proteins and although mustard was recently added to the priority allergen list, cross-reaction among seeds is not common.The most important question is “Does your child currently eat mustard?” If the answer is “no”, then there is no issue. If the answer is “yes”, the risk is extraordinarily low. I would suggest you talk to your allergist about any precautions to take if introducing mustard to his diet.

Q My daughter is 12, and just developed a peanut allergy at this age! (She had an anaphylactic reaction to trail mix.) Our family is taken aback: she never really liked peanut butter, but used to eat it occasionally. Could puberty have anything to do with this?

Dr. Waserman: There is some evidence that sex hormones may influence certain allergic diseases such as asthma. Following puberty, there is a higher incidence of asthma in young women than young men, and asthma symptoms may get worse during themenstrual cycle and then improve after menopause.
In the case of food allergy, a greater number of reported food allergies involve boys. While all of this seems to imply that hormones play a role in allergy, the mechanism is not understood and further study is needed. Peanut allergy generally starts at a younger age, however it is possible that puberty is a vulnerable time for allergy in some individuals.

Q We have a 6-year-old son with autistic disorder who has several food allergies (milk, egg, peanut). I’ve read many reports that autism is linked to food allergies. Is that valid, and if so, how do the two relate?

Dr. Watson: Autism is a disorder that affects brain development, then social interactions and communication. Autistic disorders may have a genetic link, although there may be some environmental factors which influence the condition. There is no scientific evidence that allergies cause autism.
There are studies, but of questionable quality, that link the removal of casein (dairy protein) and gluten from the diet and improved symptoms in autistic children. So this remains an area that needs study. At present, there doesn’t appear to be enough scientific support for a gluten-free casein-free diet in children with autism.
Having said that, I recognize that families may want to investigate possible triggers. Anyone considering dietary manipulation should be talking to their physician and a dietitian. In your child’s case, living without dairy is necessary because this is a diagnosed allergy. For autistic and allergic children, worsening of their allergies may worsen their behaviour.

Q At age 37, I've been diagnosed with oral allergy syndrome. It has been difficult understanding that my allergies to birch and grass are related to newfound allergies to several vegetables and fruits (including celery, carrots, tomatoes, beans, apples and grapes). My symptoms, especially with tomatoes and celery, include severe itchiness and rash around and in my mouth, as well as some tightening of the throat.
I’ve heard that some people with this syndrome can be at risk of anaphylaxis, especially to some nuts. How do you know if you’re at that level of risk?

Dr. Waserman: Oral allergy syndrome (OAS) is an allergic reaction to certain proteins found in a variety of fruits, vegetables, and nuts. This develops in some people with birch tree or ragweed pollen allergy. OAS usually affects the mouth, lips and throat, causing symptoms like the ones you are describing.
OAS occurs because the allergy-causing IgE antibody, which reacts with pollen protein, also reacts to similar proteins in the food. Cooking usually destroys the food allergens in fruits and vegetables, and those foods can then be eaten safely. Nut proteins are more resistant to cooking, and can still cause symptoms, sometimes severe.
I would recommend that fruits and vegetables that have caused symptoms only be eaten cooked. If you are eating nuts without difficulty, continue to do so. Though anaphylaxis from OAS is uncommon, nuts should be avoided if you are experiencing symptoms. See your allergist who may perform skin-prick tests and provide further information on your “level of risk”.

Q My daughter has an extreme allergy to tree nuts, and now there are so many soaps and lotions out there with shea nuts or shea nut butter or oil. I have never heard of this “nut” before. Is it a true nut? If it is, am I right to assume that my daughter should avoid the many products that contain it?

Dr. Watson: Interestingly, the shea fruit is similar in appearance to avocado. The shea tree grows in the Sahel region of West Africa. As an aside, the harvesting and processing of shea is primarily an activity of rural women (300,000 to 400,000 in Burkina Faso alone). The fruity part of the nut, when crushed, yields a vegetable oil that is used, not only in cooking, but also in soap-making and skincare and hair-care products. This is what you have seen in products.
With regard to your question as to whether or not this is a true nut, the Food Allergy Research and Resource Program reports the shea nuts are a tree nut, but that they do not belong in the list of commonly allergenic tree nuts. There are no reports of allergic reactions to shea nuts or its products. For soaps and cosmetics, it is the oil from the shea nut that is used. The oil contains little protein, which is what triggers the allergic reaction. As with everything, if you are worried or doubtful, avoid the product. I am sure there will be further information with regard to this product in the future.

Q My 5-year-old daughter has several food allergies (eggs, peanuts, sesame, peas), and recently tested allergic to fish and shellfish. In past, sometimes the only safe thing she could eat at a restaurant was French fries. But now with the fish allergy, I’m wondering: is it OK for the French fries to be fried in the same oil as fish? Some places do serve fish and chips.

Dr. Watson: The question of French fries fried in the same oil as fish is one that I have been asked for many years. In my opinion, it is not safe to eat French fries that are fried in the same oil as fish. Even though the oil is at a very high temperature, I would worry about contamination of the French fries.
I have reviewed the medical literature and cannot find any study to support this opinion, but most allergy information websites recommend avoiding French fries if they have been cooked in the same oil as fish or seafood. Why take a chance?

Q My 31⁄2 year old daughter has a tree nut allergy, confirmed by a skin test at age 2 after a reaction to a cashew. She is to return to the allergist for retesting at 4. If she still tests positive for all tree nuts, is it possible to get a RAST test for each specific tree nut? Is there a minimum age for RAST testing?

Dr. Waserman: The RAST (radioallergosorbent test) is a blood test that measures circulating IgE antibodies to a specific allergen. A positive test means you may be allergic. A negative test does not necessarily mean that you’re not allergic. There is a high false-negative rate.
It is certainly possible to do A RAST for each specific tree nut. There is no minimum age for RAST to ensure maximum sensitivity and specificity. It can be done effectively at any age.

Q My daughter has asthma and we are visiting Banff this summer. I’d like to visit the hot springs there but I understand they release hydrogen sulphide gas. Should I be concerned about this causing an asthmatic episode?

Dr. Watson: You’re correct. Hydrogen sulphide gas is released from hot springs because the hot water dissolves the minerals in the surrounding rock. It’s responsible for the odour, and this gas can also be found in some workplaces, such as sawmills.
There have been studies to see if there is a relationship between chronic exposure to hydrogen sulphide (and other sulphur gases) and asthma attacks as well as other lung diseases. In one study, there were no changes in airway function in adults with asthma who were exposed to hydrogen sulphide gas for 30 minutes when they were considered as a group, although two individuals had significant changes in airway function.It is difficult to answer your question. If your child’s asthma is well controlled, there may be little risk. I cannot say, though, that there is no risk. If you are concerned, then I would suggest that your daughter avoid the hot springs.

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Dr. Susan Waserman is an allergist and Professor in the Division of Allergy and Clinical Immunology at McMaster University in Hamilton, Ont. She is also a past president of the Canadian Society of Allergy and Clinical Immunology.

Dr. Wade Watson is a pediatric allergist and Professor of Pediatrics at Dalhousie University. He is also the head of the Division of Allergy at the IWK Health Centre in Halifax.

Ask the Allergists is a regular feature of Allergic Living magazine. If you would like to submit a question, write to editor@allergicliving.com Write "Ask the Allergists" in the subject field, keep your question brief and include an e-mail and daytime phone number.

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