Allergy to cherries: symptoms and risks

While allergy to cherries is a very rare food allergy, it still is worth mentioning and learning some information about it, including its symptoms and risks. Here is a detailed post on this topic.

What is allergy?

Allergy is a condition, or it would be more appropriate to say a number of conditions, that result from hypersensitivity reaction against a potential something in the environment that normally causes little to no problem. This potential something is named as an allergen. Allergic reaction includes hay fever, anaphylaxis, atopic dermatitis, allergic asthma, food allergies and many more. The symptoms vary from red eyes to shortness of breath, from runny nose to itchy rash. As with the symptoms the severity too varies from mild to moderate to severe and it is on the basis of this severity that preventive measures and treatment is carried out.

What is food allergy?

Food allergy is defined as an abnormal immune response of the body against food. The various risk factors are broadly classified into host factors and environmental factors. Host factors comprise of sex, age, heredity and race, most important amongst which is heredity. Environmental factors include dietary changes, environmental pollution, exposure to any infectious disease during early childhood and allergen levels in the environment.

A wide range of food can cause allergic reactions but up to 90% of allergic response to food result from soy, wheat, eggs, shellfish, milk, peanut, etc.

According to the University of Maryland Medical Center approximately 2 percent of the adults and between 4 to 8 percent of children suffer from food allergy. The food allergy symptoms are more common in children but it is not a rule of thumb. They can occur at any age. Many cases have come into limelight in which people develop allergy to foods that they have eaten for years and years without suffering any kind of allergic reaction.

Allergy to cherry

Although cherries are not amongst the top 8 food allergens (eggs, milk, peanuts, tree nuts, fish, shellfish, wheat, soy), they do result in allergic reaction in some people, especially those individuals who suffer from pollen allergies.

Throughout Europe food allergy to cherry is very common. Oral reactions are seen in people belonging to the central and northern parts, whereas, systemic reactions are more common in the Mediterranean region.

In cherry allergy the human body’s immune system reacts negatively to cherries and food containing cherries. The immune system starts producing immunoglobulin E and histamine on contact with the allergen which thus leads to a cascade of events which may even end up in the death of the individual.

Different forms of cherry allergy

Cherry allergy is frequently associated with other fresh fruits in the Rosaceae family in the Prunoideae subfamily which include peach, apricot, plum and cherry. It has two different forms.

Cherry allergy associated with birch pollen allergy

A protein in birch has similarities to cherry protein because of which people who suffer from birch pollen allergy also suffer from cherry allergy. This is more common in northern Europe. It is known as birch fruit syndrome in which the symptoms are mostly restricted to the mouth thus giving rise to a condition known as oral allergy syndrome (1). The cherry protein, specifically the allergen which is responsible for the allergy, is a heat labile protein which means that the protein cannot survive high temperature and is easily destroyed by heat. Thus cooking destroys the causative allergen. Therefore, people who suffer from cherry allergy that is associated with birch pollen allergy can enjoy cooked cherry. Such people may also develop adverse reaction to various other fruits such as apricot, pear, apple, vegetables such as carrot or celeriac (celery tuber) or nuts such as hazel nut.

According to Dr. Paul Keith, who is an investigator for AllerGen, the allergy research network, ‘When you eat the fruit raw, it’s your own body’s heat that breaks down the protein, which is why the reaction doesn’t move beyond the mouth.’

Cherry allergy associated with allergy to peach

Contrary to the above stated cause, in Mediterranean countries people who suffer from cherry allergy do not have birch pollen allergy. Instead such individuals suffer from allergy to peach. As for birch pollen, cherry and peach share a similar protein which in some individuals is considered as an allergen by the human body and thus triggers the immune reaction leading to the production of immunoglobulin E and various other chemical mediators. A cascade of events starts which leads to symptoms which are severe in intensity such as abdominal pain, generalized urticaria and vomiting.

Even these people tend to develop adverse reactions to various other fruits such as plum, apricots, apple and nuts such as walnut or hazelnut. Unlike the cherry allergen that is associated with birch pollen allergy, this particular allergen is resilient and its allergenicity survives in various processed foods such as juices and jams. It is resistant to proteases and pH induced denaturation (2).

Consequently, it was concluded by the researchers that non-specific lipid transfer proteins (nsLTPs) from cherry can elicit severe systemic reactions as the said allergen can reach the intestinal mucosa in its intact and fully active form (3). That is why people who suffer from this particular cherry allergy cannot even eat cooked cherry.

According to a research cross reactivity between cherry and peach was observed by immunoblot inhibition (4).

Allergens responsible for allergy to cherries

A study was conducted through which common epitopes on Bet v 1, the major allergen from birch pollen, and an allergen of Mr 18,000 from sweet cherry (Prunus Avium) were demonstrated. In 17 out of 19 patients the serum contained immunoglobulin E against the said allergen and it was classified as a major allergen and named as Pru a 1 (pathogen-related protein 10) (5).

And yet by another study conducted thaumatin like protein (TLP) in cherry was identified as another major cherry allergen and was designated the name Pru a 2 (23 kDa protein, a pathogen-related protein 5-similar to one in apples) (6). It results in cross reactivity against apple and grapes.

According to another study the allergic reaction in the Mediterranean people was elicited by the non specific lipid transfer protein (nsLTP) present in the cherry which has been given the name Pru a 3 (7).

In another study a fourth cherry allergen was found which belonged to the profilin protein family and was named as Pru a 4 (15 kDa protein that cross reacts to birch trees and is implicated in celery-mugwort-spice syndrome). It is an actin binding protein of the cytoskeleton. According to study the said allergen cross reacted with the Bet v 2 belonging to birch pollen, Lyc e 1 from tomato and Api g 4 of the celery (8).

Symptoms of allergy to cherries

The signs and symptoms of cherry allergy vary from mild to severe. In case of certain individuals they develop sudden allergy to cherries. As the symptoms of cherry allergy are somewhat similar to that of stomach flu or food poisoning symptoms, this allergy is one of the most often misdiagnosed food allergies. The reactions occur not only after consuming the entire fruit but also through various other products such as pudding, flavored ice cream and cherry pies.

As is true with every other allergy skin and intestines are the most commonly involved organs. Amongst various patients the symptoms can vary from severe anaphylactic reaction to abdominal symptoms, eczema, asthma or headaches (9).

Oral symptoms

Oral allergy to cherries is the most common symptom one comes across in case one is allergic to cherries. One might experience metallic taste in mouth, mouth tingling, lip swelling, tongues swelling, throat swelling and itchy mouth.

Anaphylaxis

According to Mayo Clinic, ‘Anaphylaxis is a severe, potentially life threatening allergic reaction which can occur within seconds or minutes of exposure to something you are allergic to such as peanut or venom from bee sting.’

Anaphylactic reaction to cherry has been reported but it is an unusual occurrence. According to a report, in Italy a 12 year old boy suffered from anaphylaxis after he ate cherries and exercised. As food dependent exercise induced anaphylaxis is rare this incident was concluded to have occurred due to cherry allergy.

In anaphylaxis, the respiratory and cardiovascular systems are involved and it occurs at a rapid rate.

The various chemicals that are released by the immune system during the anaphylactic reaction can cause a person to go into shock. There is sudden drop in blood pressure and narrowing of the airways which makes breathing difficult. Some other symptoms are wheezing, rapid heartbeat, swelling of the lips, tongue and the throat, rapid weak pulse, nausea, vomiting and another common symptom of allergy to cherries - rash.

Anaphylaxis is a medical emergency and can prove to be lethal if immediate medical care is not provided. It requires an immediate injection of epinephrine. Therefore, individuals who ate cherries and developed an anaphylactic reaction are advised by the doctors to carry injectable epinephrine with them at all times to use it in case an attack occurs anytime in future. As soon as the individual starts to manifest the signs of allergic reaction administer a dose of epinephrine and take the individual to the hospital for further medical treatment. If it is not treated appropriately on time the symptoms will worsen and it can lead to loss of consciousness and death.

Oral allergy syndrome or pollen food syndrome

Oral Allergy Syndrome (OAS) or Pollen Food Syndrome (PFS) is mostly seen in individuals who are allergic to pollens from weeds, grasses or trees. These pollens have proteins that are similar in structure to the proteins present in various vegetables, nuts, fruits and even spices. The most common allergen known till date responsible for oral allergy syndrome (OAS) is Bet v 1, the birch pollen because it is cross reactive to many plant foods.

Oral allergy syndrome (OAS) is a type 1 or IgE mediated hypersensitivity reaction which is sometimes called as true allergy. Raw nuts, fresh fruits and raw vegetables are a common cause of pollen food syndrome (PFS). Some people react to one or two food items only whereas others show reaction to a wide variety of food. In most instances the allergen is inactivated on cooking, processing and digestion. Consequently, in majority of the instances the symptoms are limited to the mouth and throat and occur when raw food is ingested.

People who suffer from oral allergy syndrome (OAS) experience mild itching and swelling of lips, tongue, mouth or back of throat. Burning sensation in the ear canal has also been experienced. Reactions in the eyes, nose and skin can also triggered by the allergen. On certain occasions the reaction can be very severe leading to abdominal cramps, nausea, vomiting and diarrhea. The swelling can be so severe that it may impede breathing and needs to be treated as an anaphylactic reaction. On rare occasions the presenting symptoms may be hives, wheezing and low blood pressure.

The symptoms usually start within minutes of eating and can last as long as an hour.

Other symptoms

Various other symptoms related to cherry allergy are watery eyes, sore eyes, itchy eyes, red eyes, hoarseness, wheezing, sinus pain, facial redness, facial swelling, constipation, etc.

Allergic reaction on preparation of food

Some individuals are so sensitive to cherries that even preparation of cherries causes allergic reaction such as sneezing attacks (while peeling fruit the particles get in the air), weal’s on hand (in case of broken skin the allergens penetrate) and conjunctivitis (in case you rub your eyes after peeling the fruit).

Ways to determine whether you suffer from cherry allergy or not?

It is difficult to make a clear cut diagnosis about whether one suffers from cherry allergy or not. The best way to go about it is stated in Dr. Scott Sicherer’s article in the Journal of Allergy and Clinical Immunology that was published in 2001. In the aforementioned article under the heading of ‘Diagnosis and Management’ Dr Sicherer has discussed about the clinical approach to patients with potential reactions to foods which cross-react with one another. He states that, ‘The oral food challenge remains the only modality to identify true clinical reactions.’ He also states, ‘Unfortunately, the clinician could be facing an enormous number of oral challenges with potentially severe reactions. In practical terms many patients will not undergo oral challenges but may maintain diets arrived at through their clinical history, reasoning on the basis of the available literature, and the results of tests for specific IgE antibodies.’

Before the testing is initiated comprehensive history should be taken so that undue testing would be avoided. Moreover, said individuals should be asked to keep a food diary so that a diagnosis can be made.

As oral allergy syndrome is mainly seen in individuals who have allergies to ragweed, birch or grass pollen, according to Dr. Bruce Mazer, director of the division of allergy and immunology at Montreal Children’s Hospital and an associate professor at McGill University’ ‘the key to diagnosis is the history of hay fever and positive skin tests to relevant pollens.’

In individuals who experience mild allergic reaction to cherries 

Oral provocation test

One of the ways to determine whether you suffer from cherry allergy is to eliminate cherries from your diet and then see as to if the symptoms of allergy go away or not. In individuals who did not suffer from any severe reaction to cherries initially, the allergist might suggest eating cherries again to see if the symptoms recur or not. This is known as the oral provocation test.

However, if you believe that you suffer from allergy to cherries do not elicit the test on your own without any supervision because an initial reaction which caused few problems does not necessarily mean that any future episode would be similar to it. The food which triggered only mild symptoms on the first occasion may very well cause more severe symptoms next time.

Whereas in individuals who had a serious reaction to cherries in the past oral provocation test is not advised. In such individuals following tests are performed:

Skin prick test

In the skin prick test the skin is pricked after application of prepared allergen extracts. As stated above, the allergens may be inactivated by the processing; therefore, fresh cherries are used for the test instead of using the prepared extracts. In people who suffer from allergy to fresh cherries (or any other cherry for that matter) an itchy bump will form at the site of injection within minutes. The bump will settle in about an hour. This bump is an indication that the test is positive.

Blood test for cherry specific IgE

Blood tests can also be performed.

Immunoglobulin E assay (by RAST, CAP)

It is determined to confirm the diagnosis of cherry allergy.

Fresh or frozen cherry skin test

The amount of cherry specific IgE antibody in blood can be so low that they may not be detectable. Therefore, the most helpful test is the use of frozen or fresh cherry. Best ‘senstivity and specifity’ is obtained with this test.

Prevention is better than cure

Dietary modification and allergen avoidance. In case of allergy to cherry the best and most effective treatment is to avoid eating cherries. There is nothing that works miracle other than avoidance.

In individuals in whom allergy is associated with birch pollen allergy, peeling and cooking cherries helps prevent the oral allergy syndrome as the lipid transfer protein responsible for the syndrome gets removed. Moreover, syruping removes all the allergenic proteins that are responsible for the allergic reaction in patients who are victims of pollinosis (10).

Whereas those suffering from cherry allergy associated with peach allergy, even cooking or peeling is of not much help. Such individuals have to boycott cherries for lifelong.

Some people show allergic reaction to black cherries but they have no allergy to dried cherries. So one can check whether they can tolerate a specific type of cherry even if another type causes symptoms.

According to Dr. Bruce Mazer, director of the division of allergy and immunology at Montreal Children’s Hospital and an associate professor at McGill University and Dr. Paul Keith, an associate professor of allergy and clinical immunology at McMaster University in Hamilton, Ontario, squeezing lemon juice on slices of fruit and letting it sit for a few minutes may also be an effective method to manage cherry allergy.

According to Dr. Paul Keith, for the treatment of oral allergy syndrome, the key is to manage hay fever. Using an intranasal steroid to weeks prior to the season and throughout it helps stave off seasonal increase in the allergic IgE antibodies. Nose’s production of IgE antibodies against pollen is inhibited so that when the individual is exposed to cherry proteins the allergic reaction would not occur.

According to Dr. Bruce Mazer, microwaving cherry before eating them would help prevent allergic reaction to the cherries (although not a very appetizing solution but a solution nonetheless).

People who suffer from cherry allergy even while preparing the fruit should wear rubber gloves preferably other than latex as latex has also been known to cause allergic reactions.

Immunotherapies with extracts containing birch protein have been known to improve or cure oral allergy syndrome in some patients.

Treatment in case of an allergic reaction

At the time of allergic reaction the key is to keep calm. Do not panic. Rinse mouth with plain water and rest. Lukewarm drink helps inactivate the residual allergens. Usually the swelling, tingling and itching subsides within 30 minutes up to an hour.

Eye drops are prescribed to those individuals who suffer from conjunctivitis.

Antihistamines have been known to relieve the symptoms of allergy by inhibiting the immune pathway.

Individuals who have already suffered an anaphylactic reaction are advised to carry injectable epinephrine with them at all times.

The research on allergy against cherries is still going on and a further study on the causative allergens is an ongoing process.