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Blood Test Tracker

Horse Dander IgE

Measures IgE antibodies to horse dander, which can be linked to nose, eye and breathing symptoms around horses and, less often, away from them.

AI-verified against cited sources. Awaiting expert reviewAlso called e3, e003LOINC 6143-2

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What it is

This test measures IgE antibodies to horse dander (Equus caballus, ImmunoCAP e3), the tiny flakes from horse skin and hair. The main horse allergen, called Equ c 1, is found in horse saliva and hair and is mostly breathed in. It can also travel on clothing or horsehair items, so people can be exposed without touching a horse. Horse allergens are similar to ones from cats and dogs, so people who are allergic to those animals can also have IgE to horse.

Why it matters

A detectable result shows your immune system has made IgE to horse. It can help your clinician make sense of sneezing, itchy eyes or wheezing around horses, stables or horsehair items. Sensitization is not the same as an allergy, so the result is read with your symptoms and exposure.

If it’s high

A level above your lab's range means your body has made more IgE to horse dander. It shows sensitization, which can happen with or without symptoms. The class number describes how much IgE was found, not how bad your symptoms will be.

Common causes

  • Allergy to horses, often from work, riding or living near horses
  • IgE that carries over from cat or dog allergy because their main allergens are similar
  • Indirect exposure, such as through clothing or horsehair items
  • Sensitization without any symptoms
  • A very high total IgE (above about 2,500 kU/L), which can cause a false-positive reading

What can help

  • Ask your clinician how to limit exposure, including indirect exposure through clothing
  • Ask whether testing for the horse component Equ c 1, or for cat and dog allergy, would help
  • Ask how to manage symptoms if you cannot avoid horses, such as at work

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 0–0.09 kU/L. Source: Mayo Clinic Laboratories, ARUP Laboratories, U.S. Food and Drug Administration.

ImmunoCAP IgE classes (Mayo Clinic Laboratories wording)

  • Class 0: negativebelow 0.1 kU/L
  • Class 0/1: borderline or equivocal0.1 to under 0.35 kU/L
  • Class 1: equivocal0.35 to under 0.7 kU/L
  • Class 2: positive0.7 to under 3.5 kU/L
  • Class 3: positive3.5 to under 17.5 kU/L
  • Class 4: strongly positive17.5 to under 50 kU/L
  • Class 5: strongly positive50 to under 100 kU/L
  • Class 6: strongly positive100 and above kU/L

What can affect your result

  • Cat and dog allergy, which can raise the horse result through similar proteins
  • How much contact you have with horses, stables and horsehair items
  • A very high total IgE (above about 2,500 kU/L) can cause false-positive results
  • The lab and test brand, because results from different systems are not directly comparable
  • IgE to cat and dog allergens can react with similar proteins in horse dander, which can raise the result without much horse contact (Mayo Clinic Laboratories).
  • A very high total IgE (above about 2,500 kU/L) can cause false-positive results through nonspecific binding (Mayo Clinic Laboratories).
  • Different labs and test brands give different numbers for the same blood sample, so compare results from the same lab and system.
  • Some labs reject hemolyzed, icteric or lipemic samples (ARUP).

Slow. It usually shifts over months to years, not weeks.

When to talk to a clinician

Talk with a clinician soon if you have wheezing, chest tightness or shortness of breath around horses. Call 911 or your local emergency number for severe trouble breathing, swelling of the face or throat, or fainting.

Questions you could ask

  • How should I manage exposure if I work with or ride horses?
  • Could this be cross-reactivity with a cat or dog allergy rather than horse itself?
  • Would the horse component test (Equ c 1) help?

Questions people ask

I have never been around horses. Why is my horse result positive?

Horse allergens resemble ones from cats and dogs, so IgE made against those animals can also react to horse. Allergen can also be carried on clothing or found in horsehair items. A test for the horse component Equ c 1, or your history, can help sort this out.

Are some horse breeds less allergenic?

Not that has been shown. Mayo Clinic Laboratories notes that completely hypoallergenic horse breeds have not been verified.

Show the science and sources

For clinicians and researchers

Quantitative IgE to a horse dander extract (Equus caballus, ImmunoCAP e3). Reported as allergen-specific IgE by ImmunoCAP fluoroenzyme immunoassay in kUA/L, with calibrators traceable to the WHO IgE reference (IRP 75/502). The FDA-reviewed system has a limit of quantitation of 0.1 kUA/L and reports up to 100 kUA/L; its maker recommends a 0.35 kUA/L cutoff and tells each lab to set its own range (FDA review K173726). The major horse allergen is the lipocalin Equ c 1 (e227), found in saliva, hair and some urine, with IgE to it reported in roughly 50 to 76% of horse-allergic people (Mayo, Thermo Fisher); it cross-reacts with other lipocalins, including cat Fel d 4 and dog Can f 6. As many as 30% of people with pet allergy report reactions to horses, and as many as 50% of cross-reactive sensitization may trace to horse lipocalin (Mayo). Mayo's reflex test (HRSPF) adds Equ c 1 when whole horse dander IgE is 0.10 kU/L or more. Mayo notes that completely hypoallergenic horse breeds have not been verified, and that positive results only indicate possible sensitization to horse dander or a cross-reactive allergen, while negative results do not completely exclude a reaction. Nonspecific binding can cause false positives when total IgE exceeds about 2,500 kU/L.

LOINC 6143-2 (primary). Specimen: serum.

Sources

  1. Horse Dander, IgE, Serum (test ID HORS), Mayo Clinic Laboratories
  2. Horse Dander, IgE with Reflex to Horse Dander Component, IgE, Serum (test ID HRSPF), Mayo Clinic Laboratories
  3. Allergen, Epidermals and Animal Proteins, Horse Hair and Dander (ARUP test 0055059), ARUP Laboratories
  4. Horse Dander (E003-IgE Horse Dander) (Labcorp test 602684), Labcorp
  5. ImmunoCAP Specific IgE (allergen component f447) 510(k) decision memorandum K173726, U.S. Food and Drug Administration
  6. e227 Equ c 1, horse dander (Allergen Encyclopedia), Thermo Fisher Scientific (Phadia)
  7. Specific IgE antibody criteria for Japanese cedar, Uni-CAP method (Appendix 3, in Japanese), Ministry of the Environment, Japan
  8. Allergy Testing units (LOINC Community Forum thread), Regenstrief Institute, LOINC Community Forum

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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