
==== Front
World Allergy Organ J
World Allergy Organ J
The World Allergy Organization Journal
1939-4551
World Allergy Organization

S1939-4551(24)00090-5
10.1016/j.waojou.2024.100959
100959
Letter to Editor
Self-reported garlic allergy☆
Hamadi Walaa Y. MD
Casale Thomas B. MD tbcasale@usf.edu
⁎
Division of Allergy and Immunology, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
⁎ Corresponding author. University of South Florida, 12901 Bruce B Downs Blvd, MDC 19, Tampa, FL 33612 USA tbcasale@usf.edu
24 8 2024
9 2024
24 8 2024
17 9 10095919 7 2023
17 7 2024
2 8 2024
© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
==== Body
pmcTo the Editor:

Food allergies are increasing in prevalence, some of which have not been studied. The most frequently reported and studied allergens include peanuts, tree nuts, eggs, milk, soy, wheat, sesame, shellfish, and fish.1 Garlic is commonly used in cooking worldwide yet has rarely been investigated for its allergic potential. Garlic (Allium sativum) belongs to the Amaryllidaceae (Liliaceae) family. The Allium family also includes onion, shallot, leek, scallion, and chives. Hypersensitivity to garlic has been reported as contact dermatitis,2 rhinoconjunctivitis, asthma,3 and rarely, anaphylaxis after ingestion.4

The only clinically relevant garlic allergen identified to date is alliin lyase with a molecular weight of 56 kDa. Kao et al identified alliin lyase as a major allergen of garlic in a garlic-allergic group of patients in Taiwan. Garlic alliin lyase showed strong cross-reactivity with alliin lyases from other Allium species, namely leek, shallot, and onion.5 Alliin lyase is degraded to 10 kDa when heated for 5 minutes. This allergen is found to be heat labile, and thus cooked garlic shows less allergenicity.6

This report summarizes a case series of garlic food allergic patients and describes their clinical characteristics.

The Food Allergy Research & Education's (FARE) Patient Registry was the data source for this study. It is an online repository of self-reported data collected from patients and caregivers acting on behalf of patients regarding their food allergies. As of date, the FARE registry has over 14,000 participants that have reported allergic reactions to over 200 allergens.1 Data collection is ongoing through the Invitae survey platform. Prior to data entry online, informed consent was obtained. Deidentified self and caregivers reported data from May 2017 to October 2021 from the Registry were reviewed. Demographics, co-morbidities, type of reaction, testing and treatment received were analyzed using descriptive statistics. For dichotomous variables, a fisher's p value was calculated for differences between patients with garlic allergy and those with a single food allergy other than garlic.

We identified a total of 132 patients with a self-reported garlic allergy. The prevalence of garlic allergy in the FARE registry was 1%. Of the 132 patients, 34 reported an allergy to another member of the garlic family (onion, shallot, leek, scallion, and chives) and 118 also reported another distinct food allergy. Most garlic allergic patients were diagnosed by an allergist/immunologist, 87 (66%). Skin prick testing (SPT) was the most used diagnostic test (74%) to confirm history. Blood test for food specific IgE (sIgE) antibodies was also used in about 58% of the patients. The food diary and food elimination diet were utilized in 26% and 25% of patients, respectively. Oral food challenges were infrequently performed (10%).

Demographic characteristics of garlic allergic patients were compared to 995 other FARE registry subjects who reported a single food allergy other than garlic (Table 1). Patients were mostly Caucasian with a slight skew towards the female gender in both groups. In comparison to patients in the registry with a single food allergy other than garlic, garlic allergic patients were diagnosed at a later age (59% versus 85% diagnosed at ≤ 25 years old, p < 0.01). This could indicate that garlic sensitization occurs later in life or that garlic was not evaluated as a potential source of food allergy until later. It is also noteworthy that 56% of patients with a garlic allergy identified a close relative with food allergies. In comparison, only 29% of patients with a single food allergy other than garlic identified a close relative with food allergy (p < 0.01). This suggests the possibility of a genetic role in developing garlic allergy. The top 3 comorbidities were allergic rhinitis, asthma, and atopic dermatitis. These were more frequently observed in patients with garlic allergy (p < 0.01).Table 1 Demographic characteristics of garlic allergic patients in comparison to NON-GARLIC single food allergic subjects

Table 1CHARACTERISTIC	Garlic food allergy n = 132	Single food allergy other than garlic n = 995	p-Value	
GENDER			0.507	
 FEMALE	76 (58%)	606 (61%)		
 MALE	56 (42%)	389 (39%)		
AGE AT DIAGNOSIS			0.000	
 0-25	78 (59%)	841 (85%)		
 26–65+	54 (41%)	154 (15%)		
RACE			0.636	
 CAUCASIAN	105 (80%)	809 (81%)		
 OTHER	27 (20%)	186 (19%)		
COMORBIDITIES				
 Allergic Rhinitis	52 (39%)	279 (28%)	0.008	
 Asthma	61 (46%)	318 (32%)	0.001	
 Atopic Dermatitis	62 (47%)	328 (33%)	0.001	
FAMILY HISTORY OF FOOD ALLERGIES	74 (56%)	285 (29%)	0.000	

Garlic allergy can result in serious outcomes. About 56% of patients presented to the emergency room (ER) for their reaction, 19% were hospitalized, and 6% were admitted to the Intensive Care Unit (ICU).

Though consumed frequently in a variety of dishes, few studies have investigated allergic reactions to garlic. A retrospective study assessed the presence of sIgE against garlic and onion among Saudi patients screened for the presence of food allergy. Of 108 patients screened, 15 patients (13.8%) had garlic- and/or onion-sIgE antibodies. Of those 15 patients, 12 had both garlic- and onion-sIgE antibodies. The presence of garlic- and onion-sIgE antibodies in these patients indicate sensitization and allergenic potential of these foods.7 The main complaints that prompted the testing for sIgE were abdominal cramps, urticaria, contact dermatitis, rhinitis and asthma.7 An observational cross sectional study testing garlic and onion extracts in a Spanish population was reported by Armentia and colleagues. Food hypersensitivity was detected by skin test, positive sIgE or provocation in 924 patients, and was caused by garlic or onions in 27, indicating a prevalence of 2.92%. The predominant symptoms recorded by the patients were chronic diarrhea (14.8%), dyspepsia (flatulence, poor digestion) (11.1%), and asthma (7.4%). Provocation tests in the 2 patients who agreed to them showed “labial oedema and urticaria in the first 30min after the test”. The authors concluded that there was a need to evaluate sensitization to garlic and onion in those with food allergies of unclear etiology.8

There are limitations to this report. The FARE Patient registry is voluntary and contains self-reported data which could be subjected to bias and may not represent the actual prevalence in the general population. Self-reported food allergy is often unreliable, especially for a food that is not considered a main food allergen. SPTs and sIgE were based on self-report without a double-blind placebo-controlled food challenge to confirm the diagnosis. Food diary and food elimination diet were utilized methods of diagnosis suggesting that acute allergic reactions might not have been the only reactions included.

Early diagnosis of food allergy can improve quality of life by avoiding unnecessarily restrictive diets. Data from this largest reported cohort to date of garlic allergic patients suggest that garlic and other allium species in people with food allergic reactions of unclear cause should not be underestimated as a potential source given its wide consumption. In comparison to patients in the registry with a single food allergy other than garlic, garlic allergic patients were diagnosed later, had a higher rate of family history of food allergies and were more likely to have comorbid allergic rhinitis, asthma, or atopic dermatitis. Most notably, more than half of these patients presented to the emergency department for a garlic-induced allergic reaction.

Abbreviations

FARE; Food Allergy Research & Education, SPT; skin prick testing, sIgE; specific IgE, ER; emergency room.

Funding source

None.

Availability of data

Data and materials are available. Authors are prepared to provide access to data.

Authors contributions

Walaa Hamadi: conception and design of study, acquisition of data, and analysis and interpretation of data. Drafting the article, revising it and final approval. Thomas Casale: conception and design of study, and interpretation of data. Revising and final approval of article.

Ethics statement

This manuscript is an original work and has not been published. Authors are prepared to provide access to data and materials and will retain such data for a reasonable number of years after publication. Authors ensure that this is original work and work/words of others has been appropriately cited where necessary.

Authors consent for publication

Yes, both authors, Walaa Y. Hamadi and Thomas B. Casale, consent for publication of the article.

Declaration of competing interest

None.

Acknowledgments

We thank Amy Bulson and FARE for their help in compiling data from the FARE registry.

☆ Full list of author information is available at the end of the article
==== Refs
References

1 FARE Patient Registry. Accessed September 27, 2021. https://www.foodallergypatientregistry.org/.
2 Kanerva L. Estlander T. Jolanki R. Occupational allergic contact dermatitis from alkylammonium amidobenzoate Eur J Dermatol 11 3 2001 240 243 11358732
3 Seuri M. Taivanen A. Ruoppi P. Tukiainen H. Three cases of occupational asthma and rhinitis caused by garlic Clin Exp Allergy 23 12 1993 1011 1014 10.1111/j.1365-2222.1993.tb00292.x 10779294
4 Pérez-Pimiento A.J. Moneo I. Santaolalla M. de Paz S. Fernández-Parra B. Domínguez-Lázaro A.R. Anaphylactic reaction to young garlic Allergy 54 6 1999 626 629 10.1034/j.1398-9995.1999.00806.x 10435479
5 Kao S.H. Hsu C.H. Su S.N. Hor W.T. Chang T.W.H. Chow L.P. Identification and immunologic characterization of an allergen, alliin lyase, from garlic (Allium sativum) J Allergy Clin Immunol 113 1 2004 161 168 10.1016/j.jaci.2003.10.040 14713923
6 Ma S. Yin J. Anaphylaxis induced by ingestion of raw garlic Foodb Pathog Dis 9 8 2012 773 775 10.1089/fpd.2012.1133
7 Almogren A. Shakoor Z. Adam M.H. Garlic and onion sensitization among Saudi patients screened for food allergy: a hospital based study Afr Health Sci 13 3 2013 689 693 10.4314/ahs.v13i3.24 24250308
8 Armentia A. Martín-Armentia S. Pineda F. Allergic hypersensitivity to garlic and onion in children and adults Allergol Immunopathol 48 3 2020 232 236 10.1016/j.aller.2019.06.005
