Table of Contents

f48 Onion Scientific Information Summary Allergen Epidemiology Route of Exposure Clinical Relevance Molecular Aspects Compiled By

Whole Allergen

f48 Onion

f48 Onion Scientific Information

Type:

Whole Allergen

Display Name:

Onion

Route of Exposure:

Ingestion

Family:

Amaryllidaceae

Species:

Allium cepa

Latin Name:

Allium cepa

Other Names:

Garden onion

Summary

Onion bulbs are rich in minerals, can be ingested both raw or cooked, and are used frequently as an ingredient in salads and cooked dishes worldwide. Despite their widespread dietary use, only sporadic reports exist of allergic reactions to onion ingestion, with reports of anaphylactic reactions after consumption of cooked onion being especially rare. In sensitized individuals, onion handling can induce rhinoconjunctivitis, asthma and contact dermatitis.

Allergen

Nature

Onion belongs to the family of Amaryllidaceae that includes leek, garlic, chive and rakkyo. The edible part of the onion plant is the bulb, which is rich in minerals and has a characteristic flavor. Onions are ingested both raw or cooked and are frequently used in salads and cooked dishes worldwide (1, 2). Approximately 743 million tons of onions are grown each year in more than 175 countries (3).

Taxonomy

Taxonomic tree of Onion (4, 5)
Domain	Eukaryota
Kingdom	Plantae
Phylum	Tracheophyta
Subphylum	Spermatophytina
Class	Magnoliopsida
Order	Asparagales
Family	Amaryllidaceae
Genus	Allium L.

Taxonomic tree of Onion (4, 5)

Epidemiology

Worldwide distribution

Onion allergy is rare. One study assessed the prevalence of onion sensitivity and clinical symptoms in 8109 general allergic patients. Approximately 30 % of these patients presented symptoms associated with food intake, whilst food sensitization was observed in approximately 37% of these patients. Subsequently, sensitization to onion was observed in 10 people, approximately 1% (6).

A study involving 108 patients with suspected food allergy from Saudi Arabia evaluated specific IgE levels against garlic and onion. Results showed that 13 (12.0 %) patients had specific IgE to both onion and garlic, and only one patient was mono-sensitized to onion (7).

Route of Exposure

Main

Ingestion.

Clinical Relevance

Despite its frequent consumption, allergic reactions due to onion ingestion are sporadic and limited to a small number of cases. Onions can induce both immediate and delayed hypersensitivity reactions. In sensitized individuals, onion handling can induce rhinoconjunctivitis, asthma and contact dermatitis (2).

One case study identified a 35-year-old man who had a severe systemic reaction/anaphylaxis requiring hospital treatment after ingesting cooked onions (2). Anaphylaxis was also reported in a 44-year-old patient after eating raw or lightly-cooked onions, with symptoms including intense itching, urticaria, confusion, blurred vision, transient loss of consciousness, sweating and tachycardia (8). Another patient, with a history of rhinoconjunctivitis and contact urticaria with mugwort and oral itching with peach skin, reported urticaria and oral itching after ingestion of raw onion (6).

Onions release irritating substances (thiopropanal sulfoxide and diallyl disulfide) when cut, which can cause eye irritation, respiratory and cutaneous allergic reactions. As a result, onions, along with the rest of the Amaryllidaceae family, have been implicated as a cause of occupational rhinoconjunctivitis and bronchial asthma (6).

Molecular Aspects

Allergenic molecules

Table adapted from Allergome.org (9).

Allergen	Type	Mass (kDa)
All c 3	Lipid transfer protein	12
All c 4	Profilin	-
All c alliin lyase	Alliinase	56

Allergen	Type	Mass (kDa)

The main allergens characterized for onion include All c 3 (a 12 kDa lipid transfer protein), All c 4 (a profilin), and All c Alliin lyase. The case report of anaphylaxis due to ingestion of cooked onion was likely due to the thermostable lipid transfer protein, All c 3 (2).

Cross-reactivity

Allergenic cross-reactivity has been demonstrated between members of the Amaryllidaceae family. Cross-reactivity with peach has been postulated, but findings indicate that this cross reactivity is marginal (2).

Compiled By

Author: RubyDuke Communications

Reviewer: Dr.Michael Thorpe

Last reviewed: May 2022

References

Singh A. Origin Area , Production ,Varieties, Package of Practices For Onion. 2019.
Albanesi M, Pasculli C, Giliberti L, Rossi MP, Di Bona D, Caiaffa MF, et al. Immunological characterization of onion (Allium cepa) allergy. Postepy dermatologii i alergologii. 2019;36(1):98-103.
Baloch A, Baloch S, Baloch S, Noor H, Badini S, Bashir W, et al. Economic Analysis of Onion (Allium cepa L.) Production and Marketing in District Awaran, Balochistan. 2014;5:192-205.
M. Castillo (2020). "Allergic hypersensitivity to garlic and onion in children and adults." Allergologia et Immunopathologia 48(3): 232-236
ITIS. Allium cepa L. 2022.
Armentia A, Martín-Armentia S, Pineda F, Martín-Armentia B, Castro M, Fernández S, et al. Allergic hypersensitivity to garlic and onion in children and adults. Allergologia et Immunopathologia. 2020;48(3):232-6.
Almogren A, Shakoor Z, Adam MH. Garlic and onion sensitization among Saudi patients screened for food allergy: a hospital based study. Afr Health Sci. 2013;13(3):689-93.
Arena A, Cislaghi C, Falagiani P. Anaphylactic reaction to the ingestion of raw onion. A case report. Allergol Immunopathol (Madr). 2000;28(5):287-9.
Allergome. Onion 2021 [cited 2021 6.12.21]. Available from: http://www.allergome.org/script/search_step2.php.