September 2013 Issue

Rare and Unusual Food Allergies — Learn About What They Are, What Causes Them, and the Associated Symptoms
By Sherry Coleman Collins, MS, RD, LD
Today’s Dietitian
Vol. 15 No. 9 P. 54

Allan was enjoying a family dinner of T-bone steak, mashed potatoes, and steamed vegetables. Shortly after the meal, his palms began to sweat and his body broke out in hives. His wife called the emergency nurse hotline associated with his medical insurance, who then suggested Allan go to the nearest emergency department. But Allan took an antihistamine, decided he felt better, and stayed home.

Two weeks later, Allan began experiencing the same symptoms after eating a porterhouse steak, baked potato, and half a bottle of wine. He drove himself to the nearest emergency department. Following a series of tests, the physicians couldn’t pinpoint the cause of the reaction.

However, after experiencing several more—although less severe—reactions, Allan visited an allergist. When asked whether he spends much time outdoors, Allan said yes and that he enjoys hiking and camping in the spring and summer. His allergist said he may have gotten a tick bite—the type that causes allergic reactions whenever you eat red meat.

This diagnosis may sound far-fetched, but it’s one that’s recognized as a rare food allergy affecting more people than once believed.

The Back Story
Millions of people in the United States experience food allergies and adverse food reactions. The “big eight” allergens—milk, eggs, peanuts, tree nuts, shellfish, fish, wheat, and soy—cause about 90% of reactions. However, according to the Centers for Disease Control and Prevention, more than 160 foods have caused food allergy reactions,1 demonstrating that many people react to foods that seem well outside the realm of the usual suspects. Are they true food allergies? Is there something else going on?

Let’s take a look at five rare and unusual food allergies.

Meaty Issue
Red meat allergy, as in Allan’s case, has captured the attention of the media over the past couple of years as researchers have worked to identify its cause. Because this type of allergy is so rare, it’s often overlooked and therefore underdiagnosed.

Typically, a red meat allergy involves a delayed reaction that can occur many hours after ingestion, although this isn’t always the case.2 In fact, in a study involving 24 subjects who tested positive for sensitivity to the carbohydrate alpha-galactose, symptoms were confirmed three to six hours after eating beef, lamb, or pork.2 Among these participants, common symptoms included nausea, vomiting, and diarrhea, with the most common being itching. Anaphylaxis was common in all 24 patients, which was exacerbated by exercise in at least two cases.

Diagnosing a red meat allergy can be challenging because of the delay between ingestion and symptom onset. However, a detailed history can be an important part of the puzzle. In addition, individuals with a true red meat allergy will test positive following an immunoglobulin E skin prick test. Working with an allergist is an important part of obtaining an accurate diagnosis.

Interestingly, in the above study, 80% of patients had been bitten by ticks before the onset of symptoms.2 In a different study of children between the ages of 4 and 17, nearly all who tested positive for sensitization to alpha-galactose, beef, and pork (among other potential allergens) also had been bitten by ticks.3 Researchers now believe that exposure to ticks may be the cause of this unusual food allergy. Those most likely to be affected include individuals who live in the Southeast; however, tick-induced red meat allergy has been described in locations such as Australia, too.2

Like other severe food allergies, the only treatments at this time are avoidance and symptom management with antihistamines for mild symptoms and epinephrine for anaphylaxis.

Dietitians should provide counseling on the importance of abstaining from eating the offending food as well as appropriate substitutions. Clients may need help identifying hidden sources of the food and understanding that even small amounts can provoke a serious and/or life-threatening allergic response.

Marianne Smith-Edge, MS, RD, LD, FADA, senior vice president of nutrition and food safety for the International Food Information Council & Foundation, recalls working with a client who had soy and red meat allergy and who didn’t want to believe he was allergic to beef. “He told me, ‘I can’t be allergic to red meat. I eat hamburger every day,’” she says.

The patient had visited the emergency department twice for reactions before he finally was diagnosed with the allergy. The patient’s allergist instructed him to see a dietitian and stop eating beef and soy-based foods. His dietitian worked with him and his wife, who was the primary shopper and cook, to help them understand that his food allergy was real and potentially severe. By focusing on his overall health and the benefits he’d reap by omitting red meat from his diet, he finally complied.

Raw Fruits and Vegetables
A patient once reported itching in her mouth and throat when she ate most fruits and vegetables, so she stopped eating the ones she thought were causing this reaction. Raw fruits and vegetables caused much more discomfort than cooked. It turns out the patient had severe pollen allergies for which she took prescription medication and was advised to visit an allergist to rule out food allergy.

For many people, environmental allergies such as this can masquerade as food allergies. For example, 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. They’re either cross-contaminated with birch tree pollen or 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, known as oral allergy syndrome (OAS) or pollen food syndrome.

Cross-reactivity, such as between birch tree pollen and apples, is the term used when antibodies are released in response to a protein or constituent that’s similar to the protein responsible for the true allergy. Proteins that are similar to one another can confuse the immune system, causing it to react to the wrong substance. People who experience this syndrome often aren’t taken seriously, since some clinicians assume that they’re just trying to avoid eating fruits and vegetables.

Typically, symptoms are contained in the oral cavity and are self-limiting, quickly resolving on their own once the individual stops eating the offending food. Severe reactions are possible, particularly if epiglottal swelling is involved, since this can cause breathing difficulty.4 Those who believe they have OAS should be evaluated by an allergist to rule out food allergy.

It’s common for many individuals who experience OAS to believe they’re allergic to fruits and vegetables, but they don’t have to avoid them. Dietitians should instruct clients to wash raw fruits and vegetables well or remove their skin, experiment with cooked vs. raw, and avoid the ones that continue to cause reactions. RDs can help clients choose fruits, vegetables, and other foods that are both nutritious and acceptable for regular consumption.

Spice May Not Be Nice
Dietitians know that 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. 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. Depending on the country in question, spices have become some of the most common food allergens.

For instance, a study in Spain showed that a group of 38 subjects had a clinically significant allergy to mustard.5 Like OAS, allergy to spices appears to be related to cross-reactivity to birch tree pollen but also may be associated with mugwort and ragweed pollen allergy.6 In fact, the researchers in Spain believe mustard allergy likely is linked with sensitization to mugwort pollen and other members of the Brassicaceae family (to which mustard belongs) or possibly to other unrelated plant species. Several subjects experienced food-induced anaphylaxis after eating mustard-containing foods.

In Europe, celery allergy is relatively common and therefore considered a top allergen. According to The Anaphylaxis Campaign, 30% to 40% of allergic individuals are sensitized to celery.7 Sensitization doesn’t necessarily indicate a clinical food allergy, but the potential for anaphylaxis is present. Similar to other spice allergies, celery allergy is thought to be associated with mugwort allergy.

Spice allergy symptoms are similar to hay fever, but they can be much more severe. And since spices are ubiquitous in foods, it can be difficult to identify the source of the reaction and avoid the offending spices. Dietitians must be able to help clients understand the importance of reading labels each time they purchase a product and avoid foods that may not indicate which spices have been added. Indian and Asian foods can present the most danger since they include common spices that cause allergy, so recommending that clients prepare meals at home will be helpful. The only treatment for spice allergies is to avoid the offending foods and symptom management.

Avocados, Bananas, Chestnuts, and Kiwis
According to the American Latex Allergy Association, a natural rubber latex allergy often results when sensitized individuals are exposed to one or more proteins that occur naturally in raw latex preparations. About 8% to 17% of health care workers, 68% of spina bifida patients, and less than 1% of children or adults in the general population have a latex allergy.8 Latex allergy can be severe and cause anaphylaxis.

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 Isabel Skypala, BSc, RD, and Carina Venter, BSc, PhD, RD, authors of the book Food Hypersensitivity: Diagnosing and Managing Allergies and Intolerance.6 Individuals with latex allergy have an increased risk of developing food allergy reactions, most commonly to avocados, bananas, chestnuts, and kiwis, but sensitivity to apples, carrots, celery, melons, papaya, potatoes, tomatoes, and various other foods has been recorded. 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. Treatment involves avoiding these foods once a diagnosis has been confirmed. In some hospitals, latex allergy protocol includes avoiding these commonly allergenic foods for this at-risk population.

The subject of chocolate allergy often is debated. The fact that chocolate typically is processed in such a way as to extensively dilute or remove potentially allergenic proteins indicates that most people won’t be clinically allergic to chocolate. However, Skypala and Venter suggest that this may not be the case with gourmet chocolates, which contain more of the whole cacao bean.6 In reality, it’s much more likely that individuals will be sensitive or allergic to one or more constituents of chocolate, such as milk or nuts.

Allergic reactions vary based on the true nature of the food allergy. An allergy to milk or nuts in the chocolate can result in anaphylaxis. It’s essential for dietitians to take a complete and accurate food history to determine whether someone is sensitive to chocolate or some other substance in it. If necessary, dietitians should encourage avoidance along with additional testing with a qualified allergist.

Much to Learn
The scientific community still has much to learn about food allergies, including these rare and unusual ones. Basic questions continue to go unanswered, such as what causes food allergies? Can they be prevented? Are rare reactions the result of food allergy, cross-reactivity, or some other complex immune reaction yet to be defined? For now, it’s important to remember that a true food allergy is an immune system reaction that can have severe consequences if not managed.

Since clients can have adverse food reactions to any food, dietitians shouldn’t assume that because it sounds unusual, it isn’t a real medical issue. Food allergies, like all others, can be unpredictable, so work with a qualified allergist and help clients take the necessary precautions to stay safe. Suggest they carefully read product labels and carry epinephrine with them at all times in case of anaphylaxis. And help clients put food allergy into its proper context, focusing on an overall diverse, nutritious, and liberal diet to maintain good health and a high quality of life.

— Sherry Coleman Collins, MS, RD, LD, has worked in clinical pediatrics and school foodservice, where she gained hands-on experience working with students, families, and staff to manage food allergies. She’s currently the senior manager of marketing and communications for the National Peanut Board.


1. Food allergies: what you need to know. US Food and Drug Administration website. Updated April 17, 2013. Accessed July 12, 2013.

2. Commins S, Satinover S, Hosen J, et al. Delayed anaphylaxis, angioedema, or urticaria after consumption of red meat in patients with IgE antibodies specific for galactose-α-1,3-galactose. J Allergy Clin Immunol. 2009;123(2):426-433.

3. Kennedy J, Stallings A, Platts-Mills T, et al. Galactose-α-1,3-galactose and delayed anaphylaxis, angioedema, and urticaria in children. Pediatrics. 2013;131(5):1545-1552.

4. Ausucua M, Dublin I, Echebarria M, Aguirre J. Oral allergy syndrome (OAS). General and stomatological aspects. Med Oral Patol Oral Cir Bucal. 2009;14(11):568-572.

5. Figueroa J, Blanco C, Dumpierrez AG, et al. Mustard allergy confirmed by double-blind placebo-controlled food challenges: clinical features and cross-reactivity with mugwort pollen and plant-derived foods. Allergy. 2005;60(1):48-55.

6. Skypala I. Fruits and vegetables. In: Skypala I, Venter C, eds. Food Hypersensitivity: Diagnosing and Managing Allergies and Interolance. Oxford, England: Blackwell; 2009:147-165.

7. Celery allergy: the facts. The Anaphylaxis Campaign. Allergy Factsheet.pdf. Updated November 2011. Accessed July 12, 2013.

8. About latex allergy: statistics. American Latex Allergy Association. Accessed July 12, 2013.