Tomatoes are one of the most popularly consumed fruits in the world and are used for a variety of purposes. Wild variety of tomatoes are grown in a variety of geographical regions.  They are consumed in both raw and processed forms for their richness in various nutrients. However, tomatoes are very well-known to elicit allergic reactions in sensitized individuals. Tomato allergies are often seen associated with grass pollinosis or other food or related allergies. Major clinical manifestations of tomato allergies include Oral Allergy Syndrome (OAS), urticaria, dermatitis, systemic reactions, rhinitis, abdominal pain, and anaphylaxis. Identification and characterization of tomato allergens have been studied and consist of a variety of pan-allergens like lipid transfer proteins, 1-3 β-glucanases, profilins, etc. Allergens from tomatoes show an extensive cross-reactivity to birch pollen, grass pollens, bell peppers, cherry, pineapple, banana, nuts, rubber latex, apple, celery, yellow mustard, Japanese cedar pollen, peach, and members of the Rosaceae family. Tomato sensitive individuals are advised to avoid consumption or coming in contact with tomatoes to prevent an allergic reaction.

Worldwide distribution

Tomatoes are one of the common causes of food allergy, ranging from 1.5% to 20% in the population with foodborne allergies (4). Tomato allergies have been reported in almost 1.5% of the entire population in Northern Europe, 16% in Italy and 5.6% in Germany (1, 8). Roughly about 3% tomato allergy is self-reported globally (9).

In a study, 39.2% of individuals with grass pollinosis were also allergic to tomatoes (1, 10). Similarly, 2.2- 4.3% of latex-sensitive individuals show an allergic reaction to tomatoes (1). In an epidemiological study of tomato allergy in Italy as high as 16% of people with pollen-food allergy syndrome are sensitive to allergens in tomato (11). Countries with high tomato consumption hold tomatoes as responsible for 20% of all Oral Allergy Syndromes (OAS) (3).

Food hypersensitivity was studied within students at the Finnish University. The subjects were grouped into 4 categories: with current atopic dermatitis (AD) and with and without allergic rhino-conjunctivitis (ARC) or asthma, history of AD with and without ARC or asthma, currently having ARC or asthma and without any clinically confirmed allergy. Hypersensitivity was found in 60% of the 286 students, more in women than in men and tomato accounted for 28% of these food hypersensitivities (12).

In another region-specific extensive study from 17 different clinics across 15 different countries in Europe, food hypersensitivity parameters were studied concerning 86 different types of food, tomato was the 8th most popular food for eliciting adverse allergic symptoms in sensitive individuals in Russia, Lithuania and Estonia (13). The allergenic potential of tomatoes is more dependent on cultivar and development stages than on the cultivation conditions (8).

Risk factors

Clinical allergy to tomatoes is more prevalently seen in association with other airborne or food allergies (11). The most common clinical manifestations in tomato allergy are observed as urticaria, oral allergy syndrome (OAS), dermatitis, rhinitis, abdominal pain, exercise-induced anaphylaxis. Severe allergic symptoms to tomatoes have been rarely reported (6).

Pediatric issues

Sensitization to tomato in children from a study conducted on an Italian population monosensitized to inhalant allergens ranged from 1.7% to 39%. Sensitization to tomato was reported more in children with grass pollinosis than in cases of allergy to mites (6). Sensitization to tomato is frequently reported in the pediatric and adolescent populations in Mediterranean countries (14). A 6-month-old female child with a family history of urticaria and rhino-conjunctivitis developed urticaria due to tomatoes (15). In a study involving 817 children with atopic dermatitis, (aged between 12-24 months), 24.6% of these cases showed acute urticaria by food ingestion or by contact with a range of foods. This included tomato as one of the foods, causing the allergy (16).

Worldwide distribution

Tomatoes are the fourth popularly consumed vegetables globally (5). Tomatoes are native from Central and South America and grow in Andes, Peru, Chile and Galapagos (4, 5). Wild cherry tomato, the ancestor of cultivated tomatoes, is distributed more extensively in Mexico, Bolivia, Columbia, and other regions of South America. Owing to accidental introduction or naturalization, they grow more rapidly in tropical and subtropical regions worldwide (5).

At present, tomato is cultivated in more than 150 countries. China is the main producer of tomatoes accounting for 21.8% of total tomato production followed by the USA. In the US, California and Florida are the major players in the market for tomatoes (5). Mexico, till dates, harbors the most varieties of cultivated tomatoes (3). North Europe, Canada, and New Zealand produce tomatoes under greenhouse conditions. Greece and Libya have the highest preference for tomatoes in their diet (5).

Main

The onset of allergic reactions takes place upon direct consumption of tomatoes including skin symptoms, OAS, rhinitis, or abdominal pain (8).

Secondary

Consumption of even minor quantities of tomatoes from tomato-containing products can elicit an allergic reaction (2).

Oral Allergy Syndrome

The most common clinical response to tomato allergies is seen as an Oral Allergy Syndrome (OAS), in which symptoms are seen locally at the oral mucosa (1). In Italy, a study showed that 20.6% of 262 patients with OAS showed symptoms with tomatoes (17, 18). According to studies published in the literature, OAS was most frequently reported to be the major clinical manifestation of tomato allergy in the young population with allergic pollinosis (14).

Allergic rhinitis and rhino-conjunctivitis

From a study of 113 tomato SPT-positive individuals, 18 patients reported clinical symptoms, and all showed sensitization to Artemisia and Platanus pollens. 83.3% of these 18 pollen-associated food allergic patients showed rhinitis, asthma, and/or rhino-conjunctivitis. The same study also showed that more subjects were sensitized to peel extracts (110 patients) than pulp extracts (47 patients). Individuals sensitized to both pulp and peel reported mild asthma-like symptoms than those sensitive to only peel (6). 9% of birch pollen-allergic patients showed adverse reactions to tomatoes (19). In another study based out of six allergy centers along the Mediterranean coast in Spain, out of 1734 subjects reporting for respiratory or cutaneous symptoms, 6.5% showed sensitization to tomato. 97.4% of these sensitized individuals were also sensitive to inhalant allergens diagnosed to have rhinitis, conjunctivitis or both, and other skin and lower respiratory illnesses (6).

Other diseases

Urticaria and dermatitis

Allergic reactions to tomatoes can cause skin symptoms like urticaria and dermatitis (8). Two patients were presented with urticaria every time they consumed tomatoes, which was seen to fade away once tomatoes were removed from their diet (20). Urticaria was reported as the major symptom of tomato allergy in a female-dominated study of adolescent population with allergic pollinosis and latex-allergy (14). Pollen associated food allergies have been reported to cause urticaria (21).

A case study of 39 -year-old women showed sensitization to both latex and uncooked tomatoes and potatoes that caused fingertip-dermatitis. Dermatitis aggravated upon eating only uncooked tomatoes. Along with dermatitis, she also complained of facial erythema and oral tingling (22). 29.41 % of 119 pediatric patients with atopic dermatitis showed sensitization to tomatoes (23).

Systemic reactions

Allergy to tomatoes has also known to cause systemic reactions which can cause severe effects. Some cases of allergy-induced anaphylaxis have also been reported (1, 24). Reaction to lipid transfer protein (LTP) allergens in tomato caused more severe symptoms like angioedema, dyspnea and urticaria in 15% of 40 tomato-allergic patients in Italy. These individuals also exhibited symptoms with tomato-derived products (25). Pollen associated food allergies have reported symptoms of anaphylaxis (21). Among 54 patients in a study, 48 reported at least one episode of food-dependent exercise-induced anaphylaxis and tomatoes were one of the major suspected foods (26). Eight patients between 12-27 years suffered from anaphylaxis after eating uncooked or raw tomatoes. Severe episodes of anaphylaxis were marked by larger wheal diameters during skin tests of these patients (24).

Other topic

Tomatoes contain a high level of nickel which is found to be responsible for abdominal pain, meteorism and dyspepsia in highly allergic patients. A 12-year girl was reported with these symptoms along with nausea and general malaise after consuming tomatoes (27). Patients with known Eosinophilic Esophagitis were tested for food-induced allergies and tomatoes were identified as one of the sources for allergy (28).

Allergen immunotherapy

Pollen allergen-specific subcutaneous immunotherapy (SCIT) effectively reduced the basophil activation from tomato and Japanese cedar pollen in patients with Japanese cedar pollen-tomato allergy, indicating that the therapy might be beneficial in alleviating the pollen-food allergy syndrome (PFAS). The suppression was seen over a period of 1 year in this study. A similar reduction in basophil activation has been reported in food-specific immunotherapy as well (29).

Prevention strategies

Avoidance
Tomatoes, even in small amounts, can elicit allergic reactions and thus, individuals sensitive to tomatoes are advised to avoid consumption of the fruit. This is the reason why food items containing tomatoes are asked for proper labeling in South Korea (2). However, the majority of allergic individuals can tolerate processed or cooked forms of tomatoes (30).

Author: Turacoz Healthcare Solutions

Reviewer: Dr. Fabio Iachetti

Last reviewed: November 2020