Biomarker: F306-IgE Lime

Overview

Lime is the fruit of Citrus aurantiifolia, a citrus plant in the Rutaceae family. It is encountered as fresh fruit, juice, peel, beverages, foods, and essential oils. Lime-associated reactions may include IgE-mediated sensitization or allergy, although documented immediate reactions to ingestion appear uncommon; many reported lime reactions are instead contact dermatitis or non-immune phytophotodermatitis caused by plant chemicals and ultraviolet exposure. Serum-specific IgE testing may help evaluate suspected sensitization when symptoms and exposure history suggest an IgE-mediated reaction, but a positive result indicates sensitization and does not by itself establish clinical allergy.

Clinical Use Cases

Evaluation of suspected IgE-mediated allergy: Assesses lime-specific IgE when immediate symptoms such as urticaria, angioedema, vomiting, wheezing, or respiratory symptoms occur after lime exposure.
Serum-specific IgE assessment: Provides blood-based evidence of IgE antibodies directed toward lime extract or related citrus allergens when testing is clinically indicated.
Correlation with exposure history: Helps assess whether symptoms are associated with eating lime, drinking lime-containing beverages, handling the fruit, or occupational exposure.
Differentiation of reaction mechanisms: Supports clinical distinction between immediate IgE-mediated reactions and contact dermatitis or phytophotodermatitis, which are not established by lime-specific IgE testing.
Assessment alongside other allergy testing: Results may be considered with medical history, physical examination, skin-prick testing when appropriate, and supervised oral food challenge if the diagnosis remains uncertain.
Evaluation of citrus sensitization patterns: Testing may be considered alongside selected citrus allergens when reactions occur to more than one citrus fruit, although a positive result to one citrus extract does not prove clinically relevant allergy to other citrus fruits.

Specimen Types

Serum: Commonly used for measurement of circulating lime-specific IgE.
Plasma: May be accepted by some validated laboratory methods, depending on the assay and laboratory protocol.

Measurement Methods

Allergen-specific IgE testing: In-vitro immunoassays measure circulating IgE antibodies that bind to lime allergen extract in a blood-derived specimen. Results should be interpreted with the exposure history and symptoms because the test demonstrates sensitization rather than confirmed clinical allergy.
Component-resolved diagnostics: No lime-specific molecular components are established as routine, clinically validated diagnostic targets. Published lime literature has not established a component panel that reliably distinguishes clinically relevant lime allergy from sensitization.
Skin-prick testing: May be used by an allergy specialist as an adjunct to serum testing, sometimes with a standardized extract or appropriately prepared fresh fruit material. It evaluates cutaneous reactivity and should not be interpreted independently of the clinical history.
Supervised oral food challenge: May be used when the history and sensitization tests do not provide a clear diagnosis. It is a clinician-supervised procedure rather than a blood-based biomarker test and is considered the reference approach for confirming or excluding food allergy when clinically appropriate.

Test Preparation and Influencing Factors

Fasting: Fasting is generally not required for serum-specific IgE collection unless other tests obtained from the same blood draw require it.
Medications: Most medications do not interfere substantially with serum-specific IgE measurement, although medications may affect symptoms or the interpretation of skin-prick testing. Medication review should be discussed with the clinician.
Timing of collection: Testing may be performed after a suspected reaction when clinically appropriate. The timing of blood collection should be determined by the treating clinician, particularly after a severe reaction or when symptoms are recurrent.
Clinical history: Timing of symptoms, amount consumed, preparation, reproducibility, and route of exposure determine the pretest probability and are essential for interpretation.
Sensitization versus allergy: A detectable lime-specific IgE result indicates immunologic sensitization. It does not establish that lime causes symptoms on exposure.
Total IgE concentration: Very high total IgE concentrations and nonspecific binding may contribute to false-positive or weakly positive specific-IgE results.
Age and associated allergic disease: Predictive value may vary with age, geographic setting, atopic dermatitis, and other allergic conditions. Lime-specific decision thresholds for confirming clinical allergy are not well established.
Cross-reactive sensitization: IgE binding to related citrus proteins may produce a positive result without clinically meaningful reactions to lime or every other citrus fruit.
Assay differences: Results from different assays or laboratories may not be directly comparable because testing platforms and allergen preparations can differ.
Non-IgE-mediated reactions: Contact dermatitis and phytophotodermatitis are not diagnosed by serum lime-specific IgE. Lime phytophotodermatitis is associated with furocoumarins and ultraviolet exposure rather than IgE sensitization.

Cross-Reactivity

Other citrus fruits: Immunologic cross-reactivity may occur among citrus species because of shared proteins, but clinically meaningful cross-allergy between lime and other citrus fruits is not well characterized in human studies.
Molecular components: No lime allergen components have been sufficiently characterized and validated for routine component-resolved diagnosis. Consequently, a specific protein family cannot currently be used reliably to predict clinical cross-reactivity for F306-IgE lime.
Contact allergens: Reported reactions to lime peel have involved fragrance-related substances such as oxidized limonene, geraniol, and citral. These findings primarily concern allergic contact dermatitis and should not be equated with IgE-mediated food allergy.
Clinical relevance: Sensitization to another citrus fruit or to a citrus-related extract does not prove that a person will react to lime. Symptoms must be assessed separately for each exposure, and supervised challenge may be considered when clinically necessary.
Phytophotodermatitis: Lime-associated blistering or pigmentation after skin contact followed by sunlight exposure is a phototoxic reaction involving furocoumarins, not evidence of IgE-mediated cross-reactivity.

Synonyms

Common name: Lime
Scientific name:Citrus aurantiifolia; also written Citrus × aurantiifolia
Alternative names: Key lime, Mexican lime, green lemon, sour lemon
Taxonomic synonyms:Citrus acida, Citrus lima, Citrus medica, Limonia aurantifolia
Allergen designation: F306, lime