Introduction

Choosing between extract-based IgE tests and component‑resolved diagnostics (CRD) for cat and dog dander can influence counseling, avoidance plans, and how you interpret cross‑reactivity. This page explains what each test measures, when CRD adds value (Fel d 1; Can f 1/2/3/5/6), and when a high‑quality dander extract IgE panel is sufficient for starting care.

What each test measures

• Extract IgE ("dander panels"): measures IgE to a whole allergen source (e.g., cat dander, dog dander). Extracts capture many proteins at once and are excellent screening tools for sensitization and for most treatment decisions.

• Component‑resolved diagnostics (CRD): measures IgE to individual molecules (components) such as Fel d 1 (cat) or Can f 5 (dog). CRD can clarify primary sensitization vs cross‑reactivity, refine exposure advice (e.g., male vs female dog), and help explain symptom patterns or apparent “false positives.”

Cat components you’ll see most often

• Fel d 1 (secretoglobin): the major cat allergen; dominant in most cat‑allergic patients and associated with respiratory symptoms.

• Fel d 2 (serum albumin): minor cat allergen; cross‑reacts with other mammalian albumins and can contribute to polysensitization.

• Fel d 4 (lipocalin): relevant for respiratory disease and notable for cross‑reactivity with dog Can f 6 and horse Equ c 1.

Dog components you’ll see most often

• Can f 1 and Can f 2 (lipocalins): common dog allergens; part of primary dog sensitization in many patients.

• Can f 3 (serum albumin): minor; can cross‑react with other mammalian albumins.

• Can f 5 (prostatic kallikrein): produced by the prostate and found only in male dog urine/dander; has documented cross‑reactivity with human PSA and unique counseling implications.

• Can f 6 (lipocalin): cross‑reacts with Fel d 4 (cat) and Equ c 1 (horse), helping explain multi‑mammal reactivity.

Quick reference: components vs likely clinical insights

Source	Component	Protein family	Why it matters clinically
Cat	Fel d 1	Secretoglobin	Major driver of cat respiratory allergy; high prevalence across cohorts.
Cat	Fel d 2	Serum albumin	Minor; may signal broader albumin cross‑reactivity to other mammals.
Cat	Fel d 4	Lipocalin	Linked to symptoms and cross‑reactivity with dog Can f 6 and horse Equ c 1.
Dog	Can f 1 / Can f 2	Lipocalins	Common markers of primary dog sensitization.
Dog	Can f 3	Serum albumin	Minor; may reflect multi‑mammal albumin cross‑reactivity.
Dog	Can f 5	Prostatic kallikrein	Male‑dog‑specific; cross‑reacts with human PSA; useful for exposure advice.
Dog	Can f 6	Lipocalin	Explains cat‑dog‑horse co‑sensitization (Fel d 4 / Equ c 1).

When CRD adds value

Consider adding components when:

• You need to distinguish primary sensitization from cross‑reactivity (e.g., Fel d 4/Can f 6 pattern).

• Symptoms differ by animal sex (suspected Can f 5—male dogs).

• There’s multi‑mammal reactivity (cat, dog, horse) that extract tests alone cannot explain.

• You’re correlating test results with nasal/bronchial provocation or clinical symptoms in equivocal cases.

When extract IgE is usually enough

• Screening for sensitization to cat or dog dander.

• Establishing eligibility for and designing immunotherapy with standardized pet extracts; CRD rarely changes extract selection but can refine counseling.

Evidence snapshot (what studies show)

• Fel d 1 remains the dominant cat allergen in >90% of cat‑allergic cohorts; dog sensitization often involves Can f 1 and/or Can f 5.

• Increasing numbers of positive dog (Can f 1–6) or cat (Fel d 1/2/4/7) components are associated with higher odds of symptoms (rhinoconjunctivitis/asthma) upon exposure.

• CRD can better predict clinical relevance in some settings than extract alone, potentially reducing the need for provocation testing.

How Wyndly fits into your plan

• If you already have a component or extract report, you can upload it for a physician review and a personalized plan via our Existing Test Review.

• If testing shows clinically relevant cat/dog allergy and you want a long‑term, at‑home option, our doctor‑directed sublingual immunotherapy for pets is available here: Pet Allergy Immunotherapy (SLIT). Wyndly treats environmental (not food) allergies, provides 24/7 doctor support, and ships medication to your door.

Practical recommendations (neutral)

• Start with a high‑quality extract IgE test when you need to confirm sensitization to cat/dog dander or to begin standard immunotherapy.

• Add components if: (a) you suspect male‑dog‑specific reactivity (order Can f 5); (b) you or your patient react to multiple mammals (include Fel d 4 and Can f 6); (c) extract results and symptoms don’t match.

• Use results to guide exposure counseling: e.g., Can f 5‑only sensitization may point to issues primarily with male dogs; Fel d 4/Can f 6 co‑sensitization helps explain cat‑dog cross‑reactivity even when one pet seems worse.

• Remember that test results (extracts or components) must align with clinical history; manage to symptoms and exposure, not numbers alone. Major societies emphasize that CRD complements—but does not replace—good clinical evaluation.

Key takeaways

• Extract panels are excellent for screening and for most treatment decisions.

• CRD is most useful to clarify sex‑specific dog allergy (Can f 5) and cross‑reactive lipocalins (Fel d 4/Can f 6/Equ c 1).

• Upload any prior results for review and, if appropriate, consider at‑home SLIT to build long‑term tolerance while you keep the pets you love.