— Sarah, United Kingdom Food allergies can come in groups. Plants (including fruits and vegetables) are grouped into various families, which share similar proteins. If a person becomes allergic to a protein in one plant food, they may also react to similar proteins in related plant foods. For kiwi in particular, the known relatives include banana, avocado, watermelon, cantaloupe, and peach. In addition, some people with kiwi allergy may be sensitive to latex, as the rubber tree is also in a related plant family. You should learn this list so that you can be mindful of these foods, and of latex. This does NOT mean that you are now or will ever be allergic to these other things, however. There are other variables that contribute to a person becoming allergic to something, and allergies cannot be easily predicted. If you have eaten any of the above foods since the kiwi reaction, then you have already proved that you are not allergic to them. You should continue eating them normally, as avoiding a food that causes no symptoms may actually increase your chances of becoming allergic to it in the future if you have some underlying predisposition. For the foods that you haven’t eaten since the kiwi reaction, the situation is a little more complicated. A clinician trained in food allergy would be very helpful, but allergists are scarce in the U.K. (and in parts of the United States too). The simplest approach is to be mindful of related foods and latex, but not to avoid them unless you begin to notice symptoms. You should probably avoid eating large amounts of them all at once. You should also watch for signs of latex allergy (for example, itchy, swollen mouth after going to the dentist if latex gloves are being used; itchy, swollen lips after blowing up balloons; consistent vaginal itching and swelling after condom exposure). Make sure you ALWAYS carry your EpiPen, especially when out of the house, traveling, and at special functions or catered events. Also make sure you know how to use it properly. If you have a spouse who is usually with you, make sure that person knows how to use it too. If you do not have access to an allergist, then you might ask your general doctor to send tests for IgE-antibodies that are specific (commonly called RAST tests) to each food mentioned above, as well as kiwi. You can use your kiwi result as a sort of control. If the test is negative (no antibody), that tells you that you should not trust the results of the other tests either. If the kiwi gives a high positive, then you can put a bit more credence in the others. If any of the results to the related foods are positive, then you should be especially careful about those foods, although a positive blood test does not necessarily mean that you will react to that food. Rather, a positive blood test means that you have an allergic antibody to the food and have the potential to react. The higher the level, however, the more likely you are to have symptoms. If you can see an allergist, then you might be told something different than what I am going to propose. Cross-reactivity between foods is just starting to be studied in any depth, and different allergists will give different advice because it is not yet clear what the best advice is. If I were to evaluate your condition, I would ask you if there are any foods in the list above that you have not eaten since the kiwi reaction but would like to be able to. I would then send out blood tests for IgE antibodies to each of these foods. The remaining steps should ONLY be performed by someone trained in the science of allergy. Following the blood tests, I would have you come into the office for skin testing using each of the foods in question. You could bring the fruit in a bag, although I would advise that you avoid touching the raw flesh. Skin testing would be done by using the skin test device to prick the food and then to prick your skin. If you develop an itchy welt, it suggests (but doesn’t prove) that you may react to eating that food. Then I would use the results of the blood and skin testing to help judge how careful I should be with the final part. The final step would be to have you eat the fruit in the office, beginning with very tiny amounts if the skin test was positive. This is the only way to know for sure if any of these plausible allergens cause symptoms or not. This can be time-consuming, and sometimes we can only test two or three foods a day, because one must leave sufficient time between doses to see if the person reacts. If you prove to be truly allergic and have a reaction, it can be treated immediately in-office with relatively little risk to you. Q2. Is it possible to get food allergies all of a sudden? My son has had skin tests and RAST testing for allergies. He is allergic to wheat, corn, peanuts, and rice, and his RAST test showed abnormal findings for practically everything. Before December 2006 he had no problem with eating any of these foods. It is possible to develop a small number of new food allergies in childhood (you did not give your son’s age, but I am assuming he is a child). Recent studies suggest that new food allergies can form when someone is being treated with medicines that suppress stomach acid, because the food, which may not get digested properly, would be more allergenic. It would be very unusual, however, to develop numerous food allergies, so let me list some possible explanations for what you are describing. The food allergy that is of most concern is the type caused by the formation of immunoglobulin E, or IgE, to a specific food. IgE is an antibody — that is, a protein made by the body that has various roles in the immune system. Our bodies produce different types of antibodies, like IgG and IgA, which are mostly involved in fighting infections and protecting surfaces of the body, like the lining of our intestine, that come in contact with things from the outside world. Although scientists aren’t entirely sure what the original role of IgE was, we do know that it helps protect us from parasitic infections, though it is probably involved in other important functions as well. However, IgE that recognizes food can cause allergies by triggering sudden inflammatory reactions in the body that are designed to expel the offending substance (vomiting, tightening of the lungs, coughing, runny nose and eyes, and so on). Tests for this type of IgE are called RAST tests. Although this term is no longer technically correct, since it refers to a version of the test that was performed years ago, most doctors still use this name. You should check that the RAST tests your son had were immunoassays for food-specific IgE antibodies. Other types of RAST testing — for IgG or IgA antibodies to various foods — are commercially available. These antibodies, however, are found in the blood of many people who have no problems eating the food in question, and they are believed to represent the body’s normal immune response to the food, which is not an allergy. Please check this first. You should be able to tell the type of test by the printout of the test results. Also, you might consider having the tests repeated by a different laboratory using a different testing system. These tests are sometimes not performed well by labs that are inexperienced, and results can vary between testing systems. The ImmunoCAP system, made by the company Phadia, is widely recognized as reliable. Next, if these tests were indeed food-specific IgE tests, then another possibility is that although your son does really have these allergic antibodies, he would not react to the food if he ate it. One common misunderstanding about allergy tests is that they provide yes or no results. They don’t. These tests reveal the level of an antibody that is present, but that does not tell you if it is enough to cause a reaction. The levels necessary for a reaction are different for each food. Except for the most common allergenic foods in children (peanuts, tree nuts, eggs, cow’s milk, soy, wheat, and fish), the level of an antibody that corresponds to a reaction in most people is not known. In addition, people can make many different types of IgE antibodies to food, and not all of them actually trigger allergy cells and lead to an allergic reaction. However, tests alone cannot distinguish these different antibodies. The only way to know for sure whether these positive tests really mean that your son is allergic is to have an allergist (board certified) perform a careful food challenge, a test in which the patient ingests small portions of the suspected allergen in gradually increasing amounts, under the doctor’s supervision. This is not necessary or appropriate in every situation — you must be sure that you seek a trained allergist, because few primary care doctors have been trained in the interpretation of allergy tests or know how to perform food challenges safely. Another possible explanation is that your son has a very high level of total IgE for some other reason, such as severe eczema, a parasitic infection, or a rare condition called hyper IgE syndrome. This could be determined by a test for “total IgE.” These conditions are all very unlikely, but if the total IgE levels in the blood are high enough, then food-specific tests could theoretically come back falsely positive. In short, it is unlikely that your son is truly allergic to numerous foods. But please DO NOT start feeding him the suspected allergens just to test the theory out — especially if he has been avoiding the foods for a while. That could be dangerous. Also, if you are not already working with an allergist, then I think you should ask for a referral, considering the complexity of the situation. Q3. I am allergic to vitamin E. I get skin breakouts followed by infections. How can I make sure I’m not eating foods that contain this vitamin? The most common allergic reaction to vitamin E is contact dermatitis, a form of skin allergy that generally affects areas of the skin that are in direct contact with the trigger. Noncontact areas of the skin and the rest of the body are not affected (that is, the allergy doesn’t cause wheezing, nasal congestion, stomach symptoms, and so forth). Contact dermatitis usually appears initially as a red, angry patch of skin, which can blister and ooze clear or yellow fluid. Sometimes the skin becomes infected when it is raw and open. If your reaction to vitamin E is contact dermatitis, then it is NOT necessary for you to avoid the minute amounts of vitamin E that are contained in many foods. In fact, avoidance isn’t really possible, because vitamins exist in tiny amounts in most foods and even in our own bodies. I certainly wouldn’t take oral vitamin E or buy foods that are enriched with vitamin E specifically, but I wouldn’t worry about it being in the foods you eat. If you have contact dermatitis, you would have to smear the food on your skin to have a reaction. If my description of contact dermatitis does not match your symptoms, then you may have an allergy to something else. If the problem occurs again, take a picture of the rash or broken–out skin. A photograph can be very helpful to the health care provider you may need to see to sort this out. I would begin with a dermatologist. Q4. I have had a severe reaction to the allergy test for yeast. Is this a common reaction, and if so, how do you handle it? Should I have allergy shots? — Florence, Texas By “severe reaction to the allergy test for yeast,” I assume you mean that you were tested by a board-certified allergist who used skin testing, and that this was performed by putting a drop of fluid containing yeast onto your skin and then pricking through it with a plastic or metal point. A positive reaction consists of a raised, red, itching welt at the site. People occasionally have whole-body symptoms, such as itching all over, or throat tightening, in response to allergy testing. This would be considered a severe reaction to the testing itself. If this is not what you meant, then the rest of my answer may not be applicable. Also, if you were tested using some other means, then the results of that test may not be reliable. Assuming that you had skin testing performed as described above and reacted to it in some way, then I think that your situation should be explored in more depth, because an allergy to ingested yeast is uncommon. I would try to confirm the results with blood tests for IgE antibodies that recognize yeast (usually called IgE RAST tests). Most important, the diagnosis of a yeast allergy needs to explain the symptoms that sent you for testing in the first place. Every positive allergy test needs to be substantiated by determining that an allergy to the particular food explains the person’s symptoms, since false positive tests (tests that are positive for foods that a person can eat without problems) are common. With this in mind, have you ever had clear-cut reactions to foods or beverages that contained yeast? Yeast is used in the manufacture of a wide variety of breads and commercially prepared foods, such as sauces and condiments. Can you drink beer without symptoms? Avoiding yeast altogether would not be an easy undertaking, and I wouldn’t want you to do it unless you were certain that the diagnosis was correct. Finally, there are currently no shots for the treatment of food allergies. The allergy shots currently given are appropriate for respiratory allergies, such as hay fever and asthma in response to pollens, animal and insect allergens, and molds (although not yeast). Q5. I recently underwent surgery for a deviated septum and was positive on most of my allergy tests. Every time I get a sinus infection or other allergy-related illness, I suffer from CMV and have to take Valtrex to relieve the extreme body aches. Are these conditions related? — Rebecca, Georgia I suspect that whenever you get run down with a sinus infection or have severe allergy symptoms, your immune system is working in overdrive and it is not able to keep the CMV fully suppressed. CMV stands for Cytomegalovirus, a virus in the herpes family that can cause symptoms of fatigue, body aches, sore throat, and fever. Many carry the virus in their bodies but don’t have symptoms. I don’t believe there is a more specific connection between allergies and CMV, but the same thing can happen to patients who are prone to recurrent cold sores (caused by a herpes virus): They report getting outbreaks of lip blisters during or just after a sinus infection or prolonged severe allergy symptoms. I would anticipate that an illness of any type — allergic or otherwise — would make you more likely to have a flare-up of CMV. Also, please consider these two points about your situation: Perhaps you should speak to the clinician who helps you manage your CMV infection and find out if there is a way to confirm that the body aches you experience are definitely due to CMV. It is not unusual for people with sinusitis or even just severe allergies to feel achy and tired as part of the process. You are attributing these symptoms to CMV because the CMV gave you similar symptoms in the past, but the body aches may be just something your body does when it’s run down. It is possible that if you waited a few more days, you would get better without the Valtrex. On the other hand, if your doctor agrees that the CMV is the most likely cause of your body aches, and it happens predictably each time you get sick, then maybe you should talk about starting the Valtrex in anticipation, whenever you get a significant illness. That might make the process smoother for you. Q6. My 11-year-old son has been testing positive for multiple food allergies by skin test forever, but recently he had allergy blood tests and they were all negative. Is it possible he doesn’t have them anymore, or do I need to do the skin test also? The only definitive test to diagnose food allergy is the double-blind, placebo-controlled challenge. In this test, the allergist gives the patient capsules to ingest. Some contain the suspected allergen and some don’t. Neither the patient nor the doctor knows which is which; that’s why it’s called “double-blind.” After each capsule, they watch to see if an allergic reaction develops. Depending on your child’s symptoms in the past, it would be worthwhile to see the results of his blood and skin tests in order to determine if this type of challenge is the next step. You don’t mention the specific foods he was allergic to, but it’s worth pointing out that it is unusual to outgrow peanut, tree nut, and shellfish allergies. Q7. For years I’ve been suffering from allergies and intolerance to foods and inhalants. With global warming, the symptoms start earlier in the year and last longer. I seem to become more and more sensitive to foods. My symptoms range from migraines to dizziness, sensitive eyes and fatigue. I also get stomach pains and bloating. Do you know of any tests that can identify the intolerances? And have any new medicines been developed that could help me? Thanks for your help. There are accurate tests to diagnose food allergy, including skin tests and blood tests (RAST), but limited tests to evaluate food intolerances such as lactose intolerance. A food intolerance is an abnormal reaction to a food that, unlike an allergy, doesn’t involve the body’s immune system. For now, the best thing to do is maintain a food and symptom diary so that you can map out which food results in any sort of discomfort. That way, you can track the cause and effect. The only treatment for food allergy is to avoid the food that causes the reaction. This is also the best way to handle most cases of food intolerance. However, in the case of lactose intolerance, you can boost your tolerance by taking a supplemental lactase enzyme before consuming dairy products. Also, some people can’t break down the complex carbohydrates in beans and benefit from taking alpha-galactosidase pills – sold over the counter in many stores – to minimize symptoms of gas. Q8. My son-in-law is allergic to peanuts. Should his children (my grandkids) get tested? One is 3 years old and the other is 7 months. Are there any other precautions we should take? This is a tricky situation because your grandchildren may not show a positive allergy test (skin prick test or blood test) until they have actually eaten a peanut or something made with peanuts. Children who are allergic to peanuts will usually have their first reaction between the ages of 1 and 2. If your grandchildren see an allergist, the first step would be a skin test, in which the skin is pricked and exposed to small amounts of peanut protein to see if any hives develop. If this test is negative, then an oral challenge – ingesting a suspected allergen under close supervision – would be the next step. As a grandparent, the best precaution you can take is to educate yourself about peanut and other food allergies so you know which foods to avoid and so you can watch for symptoms (skin rash or hives, difficulty breathing, nausea and others) when the children are with you. Q9. My son has white patches on his arm/elbow area and behind his knees that he scratches a lot. Is that a sign he has food allergies? If your son’s physician has diagnosed him with atopic dermatitis (eczema), you should be informed that food allergy is an important trigger of atopic dermatitis in infants and young children. Q10. There are so many allergy tests out there, and I’ve heard some of them are not even accurate. Is there an accurate way to find out what foods I might be allergic to? Many different types of tests for food allergies are performed in the community, but only a few are considered valid by mainstream Western medicine. The tests that have been shown to accurately diagnose food allergies and that are recommended by the American Academy of Allergy, Asthma, and Immunology — the largest professional organization of allergists in the United States — are the following:
- Skin testing. Skin testing involves placing drops of purified liquid from possible allergenic foods on the skin and pricking the skin with a tiny plastic or metal point to allow the liquid to penetrate. The prick is not enough to draw blood and is only momentarily uncomfortable. A positive test — which means that allergy to that food is possible — looks like a mosquito bite and appears within ten minutes. It typically disappears within an hour.
- Immunoassays for food-specific IgE. The immunoassay is a simple blood test that looks for allergic antibodies to specific foods.
- Physician-supervised challenges. Generally performed only after one or both of the tests above have already been conducted, this test involves having the potentially allergic person eat the food in question under medical supervision. The first two types of tests listed above detect immunoglobulin E (IgE), an abnormal protein that is produced in people allergic to specific kinds of food. The third type of test is used to safely verify the presence of a food allergy when the former methods are not definitive. The most serious form of food allergy is an IgE-mediated food allergy, since it can cause a severe, whole-body reaction known as anaphylaxis. Anaphylaxis is a very dangerous reaction that usually involves some combination of the following symptoms: Itching, flushing, swelling of the lips or face, difficulty breathing, throat closure, and low blood pressure Tests for food allergies that have not been shown to be reliable include:
Immunoassays for food-specific IgG and IgA. These tests detect antibodies to food that are not known to cause allergy or any other diseaseBasophil-activation test. This involves testing a person’s blood in a test tube to see whether a certain type of cell is activated by the presence of a certain food. The test has not been shown to reliably detect food allergy.Provocational/neutralization test. This test involves exposing a patient to a food — usually not by ingestion — and measuring some unrelated factor, such as muscle strength.
Some of these unproven tests are offered by alternative medicine providers. Others are blood tests that are advertised to doctors as well as directly to patients over the Internet. One concern about these tests is that they detect food allergies in people who are not really allergic. This is especially common in growing children. People could also be told they are allergic to one food, when in fact they are allergic to something different — they could then have a serious reaction in the future. Q11. I have different reactions to different foods. I have cut out so much food that showed up on my skin test years ago. I get palpitations, hives, shortness of breath, backaches, mouth sores, and dizziness. I stay away from my triggers, but just sometimes…I need to cheat!! I’m 46 and it’s not easy when I have to make different meals for the rest of my family. So does that mean I’m allergic to these foods or just a food sensitivity? Because how could it be that I could be allergic to so many different foods? — Mimson It is rare for adults to truly be allergic to multiple foods. The most common symptoms of dangerous food allergy (i.e., the type that can progress to anaphylaxis, a life-threatening whole-body allergic reaction) are the following:
Itching in the mouth, lips, throatHives, flushing/redness, skin swelling (of the lips and face is particularly common)VomitingWheezing or asthma symptomsChange in voice quality and throat tightnessSudden onset of nasal congestion and redness of eyesDiarrhea and abdominal crampingDizziness and a sense that you might faintLoss of consciousness
These symptoms generally begin minutes after eating the culprit food, although it is possible for symptoms to be delayed for up to two hours. Mouth sores and back aches are not typical symptoms of a food allergy. Another thing to consider is the type of hives (urticaria) you suffer from. Do they only occur once in a while, right after eating, or are your hives a problem that has come and gone over the years? If the latter is a more accurate description of your problem, than you likely have chronic urticaria. For most people with this problem, there are no specific underlying allergies. A problem in the practice of allergy is the over-interpretation of allergy skin testing. Allergy tests are not yes/no types of tests. A positive skin test means that the person has IgE antibodies to the food in question and so he or she could, in theory, react to it. A positive test does NOT mean that the person will definitely have a reaction when that particular food is eaten. There are other factors involved that cannot be easily measured. Skin test results must therefore always be reviewed in detail, to see if any of the foods that tested positive have actually caused symptoms in the past. If the person does not recall, then it may be necessary to perform supervised food challenges, or eliminate one food at a time from the diet to see if there is any change over time. I would recommend that you find a board certified allergist in your area and get re-evaluated. If possible, choose a practice that is hospital-based, as doctors practicing in this setting are more likely to be able to perform physician-supervised food challenges, if this turns out to be necessary. Board certified allergists are listed on the website of the American Academy of Allergy, Asthma, and Immunology. There is a section called “Find an allergist” that allows you to search for one in your area. When you call to schedule an appointment, be sure to ask for someone in that practice who has an interest in food allergy. Learn more in the Everyday Health Allergy Center.
