Cat and Dog Allergy: Symptoms, Allergy Tests and Real Relief

A dog allergy or cat allergy is an immune reaction, in people, to tiny proteins that dogs and cats shed in their skin flakes (dander), saliva and urine. This guide is about humans who are allergic to pets, not about allergies in dogs. Typical signs are sneezing, a runny or stuffy nose, itchy red eyes, coughing and, in people with asthma, wheezing or chest tightness, often within 30 minutes of contact with the animal.

Pet allergy is common: Cleveland Clinic estimates that up to 3 in 10 people in the US are allergic to cats and dogs, and that cat allergy is more than twice as frequent as dog allergy. A skin prick test or a specific IgE blood test confirms it, and component tests such as Fel d 1 or Can f 5 can show which protein you react to. There is no truly hypoallergenic breed, but cleaning, air filtration, medicines and allergy injections can make life with, or near, a pet much easier.

Key takeaways

• The allergy comes from proteins in dander, saliva and urine, not from fur itself, so no dog or cat breed is truly hypoallergenic.
• Fel d 1 is the main cat allergen: more than 90% of cat-allergic people react to it. In dogs, Can f 1 and Can f 5 are the most common culprits.
• A skin prick test (read in 15 to 20 minutes) or a specific IgE blood test confirms sensitisation; only your symptoms turn it into an allergy.
• Pet allergy is a major trigger of asthma; reacting to several dog or cat proteins goes with a higher asthma risk.
• HEPA air cleaners, keeping pets out of the bedroom, antihistamines, nasal steroids and allergy injections all help; new anti-Fel d 1 antibodies are in phase 3 trials.

What is a dog or cat allergy?

In an allergy, the immune system treats a harmless protein as a threat. It makes immunoglobulin E (IgE) antibodies against it. The next time you breathe in the protein, IgE on mast cells triggers the release of histamine and other chemicals that cause sneezing, itching, swelling and airway narrowing. Our guide to the allergy blood test and IgE explains this mechanism in more detail.

The Asthma and Allergy Foundation of America (AAFA) estimates that allergies to cats and dogs affect 10% to 20% of the world's population, and about 6 in 10 US households have a pet. A 2026 review notes that cat allergy reaches 30% of the population in some regions.

Pet allergy in people versus allergies in dogs

Searches for "dog allergy" mix two very different problems. This article covers people who react to dogs or cats. Dogs can also have their own allergies (to fleas, food or pollen), which a vet treats. If your dog is the one scratching, see your vet; if you are the one sneezing around dogs, read on.

Cat and dog allergens: Fel d 1, Can f 1 to Can f 6 and dander

Allergens are named after the animal's Latin name: Fel d for Felis domesticus (cat) and Can f for Canis familiaris (dog). According to a review by Curin and Hilger, they fall into a few protein families that explain cross-reactions.

Cat allergens

• Fel d 1 is the major cat allergen. More than 90% of cat-allergic patients recognise it, and it accounts for 50% to 90% of the allergenic activity of cat dander. Cats make it mainly in saliva and spread it onto their coat when they groom, so it ends up on hair and skin flakes that float in the air.
• Fel d 4 is a lipocalin recognised by 63% of cat-allergic people. Along with Fel d 1, it is linked to the development and severity of asthma.
• Fel d 2 is cat serum albumin. It cross-reacts with albumins from other mammals and is responsible for the rare "pork-cat syndrome", a reaction to pork meat in people sensitised to cat.

Dog allergens

• Can f 1, a lipocalin, is the major dog allergen, recognised by 49% to 75% of dog-allergic patients. Can f 2, Can f 4 and Can f 6 are other lipocalins; Can f 6 cross-reacts with cat Fel d 4.
• Can f 3 is dog serum albumin, which cross-reacts with other mammals' albumins.
• Can f 5 is a kallikrein made in the prostate of male dogs. About 70% of dog-allergic patients recognise it. It is similar to human prostate-specific antigen (PSA), which may explain rare reactions to human semen in some women.

The proteins are sticky and travel. Curin and Hilger report cat and dog allergens in homes without pets, in schools and on public transport: they ride on clothes and stay airborne for a long time. The American College of Allergy, Asthma and Immunology (ACAAI) adds that cat dander stays airborne at least 30 minutes after being disturbed.

Pet allergy symptoms

Symptoms look like hay fever, but they can occur all year round. Cleveland Clinic lists:

• sneezing and a runny or stuffy nose;
• itchy, watery or red eyes (see our guide to conjunctivitis causes and treatment);
• a scratchy throat or mouth and coughing;
• hives or itchy skin where a pet licked or scratched you;
• shortness of breath, wheezing or worse asthma;
• tiredness from congestion and poor sleep.

Timing varies. In severe allergy, symptoms can start within 30 minutes of exposure; in milder allergy, they may appear a few hours or even a few days later. They usually fade within hours after you leave, but can last several days. Constant congestion from a pet at home is easy to mistake for a sinus infection.

Pet allergy often goes together with other allergic conditions such as eczema and hay fever. Our guide to eczema symptoms and triggers explains why allergies and eczema often go together, and the guide to skin rash causes and warning signs helps sort out other rashes.

Pet allergy and asthma

Allergy to cats, dogs or both is considered a major risk factor for asthma and rhinitis, according to an international workshop report in the Journal of Allergy and Clinical Immunology. AAFA notes that an asthma episode can begin within 15 to 30 minutes of breathing in the allergen.

The number of proteins you react to matters. In a 2026 Swedish study of 595 young people aged 19, the share reporting asthma on contact with a dog rose from 0.9% in those sensitised to no dog molecule to 40% in those sensitised to six. Asthma was mostly tied to the dog lipocalins (Can f 1, 2, 4, 6), while Can f 5 was linked more with nose and eye symptoms. If you have asthma, our guide to asthma symptoms, diagnosis and treatment covers inhalers and action plans.

Who gets a pet allergy, and can it start later in life?

Your risk is higher if your parents have pet allergies. Pet allergy can also start in adulthood. In the European Community Respiratory Health Survey, 6,292 adults aged 20 to 44 who were not sensitised to cats were retested 9 years later: 3.7% had become sensitised. Getting a cat during that time nearly doubled the risk (relative risk 1.85), especially in people already sensitised to other allergens. Having had a cat in childhood was protective.

That fits with research on early life. In a Finnish cohort of 3,781 children, having a dog at home during the first year was linked with less asthma by age 5 (hazard ratio 0.60), and having a cat with less eczema (odds ratio 0.68). Researchers tie tolerance to cats in childhood to high levels of IgG4 antibodies. These are associations, not proof that getting a pet prevents allergy, and a Danish cohort of high-risk children found no link either way, so the evidence is not strong enough to recommend getting a pet to prevent allergy.

How is a dog or cat allergy diagnosed?

A doctor or allergy specialist starts with your history (what happens, how fast and where), then tests for IgE against cat or dog proteins.

Skin prick test

Drops of cat or dog extract are placed on the forearm or back and the skin is pricked through them. A positive result is a raised, itchy bump (wheal), read after 15 to 20 minutes. MedlinePlus notes that the larger the reaction, the more likely you are allergic. You may need to stop antihistamines beforehand.

Specific IgE blood test (dog and cat dander IgE)

A blood sample is tested for IgE against cat dander (code e1) or dog dander (code e5). It is a good choice if you have widespread eczema, cannot stop antihistamines or are at higher risk of a severe reaction. MedlinePlus explains that a high specific IgE suggests sensitivity, but the amount does not predict how serious your allergy is, and false positives occur. Cleveland Clinic estimates that 50% to 60% of positive allergy blood tests do not correspond to a real allergy. Results usually take a few days.

Component-resolved diagnostics: Fel d 1, Can f 1, Can f 5

Instead of a whole-dander extract, component tests measure IgE to single proteins. They help when you react to both cats and dogs, or before allergy injections. A Spanish study found that 16.1% of patients positive for cat components and 27.6% positive for dog components had a negative skin prick test, so components can catch missed sensitisation.

Components also give practical clues:

• Fel d 1 positive: genuine cat allergy, the main target of cat allergy injections.
• Fel d 4 or several dog lipocalins positive: higher asthma risk.
• Fel d 2 or Can f 3 (albumins) positive: cross-reaction between furry animals, and possibly with pork.
• Can f 5 positive alone: you may react to male dogs only. In a small Danish trial, all 7 teenagers sensitised only to Can f 5 reacted to male dog extract on skin testing, but only 1 reacted to female dog extract.

Pet allergy test results: reference values

Specific IgE is reported in kilo-units per liter (kU/L, the same as kUA/L). The classes below are the international scale summarised by DermNet; your own report's range is the one that counts. Some laboratories and studies use a lower 0.10 kU/L threshold.

How to read your dog and cat allergy test results

A positive test means sensitisation: your body makes IgE against the animal. It becomes an allergy only when it matches your symptoms. Keep these points in mind:

• A class 2 or 3 result with sneezing at every visit to a cat owner is convincing; the same value without symptoms may need no treatment.
• A negative test does not rule out every cause: dust mites, mould and pollen cause the same nasal symptoms. A dog dander test also targets mainly Can f 1 and may miss other dog proteins, as Testing.com points out.
• A high total IgE or high eosinophil count supports an allergic background, but parasites, smoking and other diseases can raise them too.
• If your eosinophils are high and you have asthma, they also guide treatment, as explained in our news piece on eosinophils and asthma treatment.

Severe whole-body reactions (anaphylaxis) to animals are rare but have been reported. After a suspected anaphylaxis, doctors sometimes measure serum tryptase to support the diagnosis.

The hypoallergenic dog and cat myth

Poodles, Labradoodles, Portuguese water dogs and some terriers are often sold as hypoallergenic. The science does not support the label:

• A Dutch study measured Can f 1 in 196 so-called hypoallergenic dogs and 160 other dogs. Hair and coat samples from the "hypoallergenic" breeds actually contained more allergen, and airborne levels in homes did not differ between breeds. The authors concluded there is no evidence to call any breed hypoallergenic.
• A US study of homes in a Detroit-area birth cohort found no difference in dog allergen in house dust between "hypoallergenic" and other breeds.
• For cats, ACAAI notes that hair length, sex and time spent indoors are not associated with allergen levels, while homes with more than one cat have more.

Individual animals differ, though: a person sensitised only to Can f 5 may tolerate a female dog better, as the Danish trial suggests. Spending several hours with a specific animal before adopting it is the most reliable test.

Avoidance and cleaning: what works at home

Removing the pet lowers exposure the most, but allergens linger: AAFA says pet allergens can cause symptoms up to 6 months after the animal is gone, especially cat allergens. Most people prefer to keep their pet and reduce exposure. Steps recommended by AAFA, ACAAI and Cleveland Clinic:

• Keep pets out of the bedroom, where you spend a third to half of your time, and off beds and sofas.
• Run a HEPA air cleaner, ideally in the bedroom, at least four hours a day.
• Vacuum carpets and fabric furniture at least once or twice a week with a HEPA or microfilter vacuum; consider hard floors.
• Wash rugs and bedding weekly in hot water; damp-dust hard surfaces.
• Bathe the dog or cat about once a week, and have someone without the allergy brush it outdoors.

A cat food containing an anti-Fel d 1 antibody from eggs (IgY) is also on the market. In a 12-week study of 105 cats by the manufacturer's researchers, active Fel d 1 on the cats' hair fell by 47% on average by week 10 (range 33% to 71%). Its effect on human symptoms needs independent study.

Pet allergy treatment: medicines

Medicines treat symptoms but do not cure the allergy. Options described by Cleveland Clinic:

• Oral antihistamine pills such as cetirizine start working in about 30 minutes; a daily antihistamine may be advised if you are around animals often.
• Antihistamine nasal sprays act within 15 to 30 minutes.
• Nasal corticosteroid sprays calm inflammation in the nose but may take at least two weeks to help.
• Montelukast, a leukotriene blocker, carries an FDA boxed warning (2020) about serious mood and behaviour changes; for nasal allergies the FDA says it should be reserved for people who do not respond to or cannot tolerate other allergy medicines.

Allergy injections and other immunotherapy

Allergen immunotherapy is the only treatment that changes the immune response itself. Small, rising doses of cat or dog extract are injected under the skin. Cleveland Clinic describes a build-up phase of one to three injections a week for six to 10 months, then maintenance injections about once a month. You stay 30 minutes in the office after each injection. About 80% of people treated with allergy injections see a significant improvement, and about 60% keep lasting benefits after three to five years of treatment.

For pets, results are more mixed than for pollen or dust mites. A 2024 Italian review explains that cat and especially dog extracts are poorly standardised, which limits their effectiveness, and that component testing helps choose the right patients. A 2026 review adds that cat immunotherapy, by injection or under the tongue, can improve cat-induced asthma and rhinitis, and that extracts containing Fel d 4 as well as Fel d 1 look promising. An Italian analysis of 1,403 component tests suggests that immunotherapy is likely ineffective in people sensitised only to Can f 5.

When to see a doctor

See your GP or an allergy specialist if:

• you sneeze, cough or have itchy eyes around pets for weeks, or symptoms disturb sleep or work;
• you wheeze, feel chest tightness or need your reliever inhaler more often around animals;
• medicines from the pharmacy do not control your symptoms;
• you have asthma and are thinking about getting a pet.

Call 999 for trouble breathing, wheezing that does not improve with your reliever inhaler, swelling of the lips, tongue or throat, widespread hives with dizziness or fainting: these can be signs of a severe asthma attack or anaphylaxis.

Latest scientific advances in dog and cat allergy

Antibodies that neutralize Fel d 1

Researchers have designed monoclonal antibodies that bind Fel d 1 before it reaches IgE. In a 2022 randomized trial in 56 cat-allergic adults with mild asthma, a single injection of the antibody pair REGN1908/1909 prevented the drop in lung function on cat allergen exposure from day 8 up to day 85, and patients tolerated three times more allergen than with placebo. A larger phase 3 trial at home (NCT04981717) was stopped early; a new phase 3 trial (NCT07675811), recruiting since July 2026, is testing the antibodies for cat-allergic eye symptoms in 570 participants aged 8 and over.

Component tests predict asthma risk

The 2026 Swedish study of 19-year-olds showed that the number of dog and cat proteins you react to tracks with asthma on animal contact, and that Can f 5 was the most common dog sensitisation (51.6%) while Fel d 1 dominated in cats (91.2%). A component test can show whether a positive dander result is likely to matter for your lungs.

Air cleaners proven in a chamber trial

In a 2025 randomized trial, 30 cat-allergic adults with mild asthma breathed cat allergen for two hours in an exposure chamber. With a HEPA air cleaner running, airborne allergen fell from 79.6 to 14.2 ng/m³; no one had an early asthma attack in the first 50 minutes, against 53.3% with a placebo cleaner, and nose and eye symptoms fell by 52.2%. It supports running one in the bedroom of a cat owner with asthma.

Better cat immunotherapy

A 2026 expert review argues that cat immunotherapy is underused, partly because extracts vary, and that adding allergens beyond Fel d 1, such as Fel d 4, or combining immunotherapy with antibodies may improve results. Trials of injections into lymph nodes (intralymphatic immunotherapy), such as NCT06960382 in Zurich, are also under way.

Which tests can help?

Tests often ordered when a pet allergy is suspected:

• a skin prick test to cat and dog extracts, with other indoor allergens such as dust mites and mould;
• specific IgE to cat dander (e1) or dog dander (e5), then components (Fel d 1, Fel d 2, Fel d 4, Can f 1 to Can f 6) when needed;
• total IgE and a complete blood count with eosinophils;
• spirometry (lung function testing) if you cough or wheeze around animals.

Glossary

• IgE: the antibody behind allergic reactions; specific IgE targets one allergen.
• Sensitisation: having IgE against an allergen, with or without symptoms.
• Fel d 1: the major cat allergen, made mostly in saliva.
• Can f 1 and Can f 5: a common dog lipocalin allergen, and a protein from the prostate of male dogs.
• Component-resolved diagnostics: blood tests for IgE against single purified allergen proteins.
• Allergen immunotherapy: allergy injections or tablets that build tolerance over years.

Frequently asked questions

What are the symptoms of a pet allergy?

Sneezing, a runny or stuffy nose, itchy watery eyes, cough, an itchy rash or hives where the pet touched you, and wheezing or shortness of breath in people with asthma. They can start within 30 minutes or build up over days.

What makes a dog hypoallergenic?

Nothing reliable. Allergens come from skin, saliva and urine, not fur, and studies found as much or more Can f 1 on "hypoallergenic" breeds, with no difference in home air or dust.

Are there hypoallergenic cats?

No cat is allergen-free; all cats make Fel d 1. Levels vary between individual cats, and homes with more than one cat have more allergen.

Can you develop a pet allergy later in life?

Yes. In a European study of adults followed for 9 years, 3.7% newly became sensitised to cats, and getting a cat nearly doubled that risk, especially in people with other allergies.

How long does cat dander stay in a house?

Pet allergens can cause symptoms for up to 6 months after the animal leaves, especially cat allergen, according to AAFA. Cleaning and HEPA filtration help.

Can you live with a dog if you are allergic?

Often, yes, with a dog-free bedroom, HEPA filtration, regular cleaning and bathing, medicines and, if needed, allergy injections.

Blood test or skin test for pet allergy: which is better?

Both detect IgE against cat or dog proteins. The skin test gives results in 15 to 20 minutes and, according to Cleveland Clinic, tends to be more accurate; the blood test suits people with eczema, those who cannot stop antihistamines, and young children, and allows component testing.

Can allergy injections cure pet allergy?

They can reduce symptoms for years after treatment, but results for pets are less consistent than for pollen, especially for dogs. About 60% of people keep lasting benefits after three to five years of injections in general; ask an allergy specialist whether your test profile makes you a good candidate.

Sources

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• Curin M, Hilger C — Allergy to pets and new allergies to uncommon pets — Allergol Select, 2017 — pmc.ncbi.nlm.nih.gov
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• Schoos AM et al. — Children Monosensitized to Can f 5 Show Different Reactions to Male and Female Dog Allergen Extract Provocation: A Randomized Controlled Trial — J Allergy Clin Immunol Pract, 2020 — doi.org
• Roger A et al. — Using Component-Resolved Diagnosis to Characterize the Sensitization to Specific Cat and Dog Allergens in Patients with Allergic Respiratory Diseases in Catalonia, Spain — Int Arch Allergy Immunol, 2023 — doi.org
• Olivieri M et al. — Risk factors for new-onset cat sensitization among adults: a population-based international cohort study — J Allergy Clin Immunol, 2012 — doi.org
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• Gherasim A et al. — Efficacy of air cleaners to reduce allergic responses to cat: A randomized clinical trial using an environmental exposure chamber — Respir Med, 2025 — doi.org
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• Villalta D et al. — Frequency of allergic sensitization to Can f 5 in North East Italy. An analysis of 1403 ISACs 112 — Eur Ann Allergy Clin Immunol, 2019 — doi.org
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• Regeneron Pharmaceuticals — Fel d 1 monoclonal antibodies in allergic conjunctivitis due to cat allergy (phase 3) — ClinicalTrials.gov, 2026 — clinicaltrials.gov
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• MedlinePlus — Allergy Skin Test — National Library of Medicine — medlineplus.gov
• MedlinePlus — Eosinophil count, absolute — National Library of Medicine — medlineplus.gov
• Cleveland Clinic — Allergy Blood Test — Cleveland Clinic — my.clevelandclinic.org
• Cleveland Clinic — Allergy Shots: Effectiveness, Side Effects and What To Expect — Cleveland Clinic — my.clevelandclinic.org
• DermNet — Immunoglobulin E tests — DermNet — dermnetnz.org
• US Food and Drug Administration — FDA requires Boxed Warning about serious mental health side effects for asthma and allergy drug montelukast — FDA, 2020 — fda.gov
• Testing.com — Dog Dander Allergy Test — Testing.com — testing.com
• NHS — Allergies — National Health Service (England) — nhs.uk

Further reading

• Allergy blood test: IgE and panels explained
• Asthma: symptoms, causes, diagnosis and treatment
• Eosinophils: high, low and normal levels
• Conjunctivitis (pink eye): causes and treatment
• Eczema: symptoms, causes and treatments
• Serum tryptase: levels, causes and meaning
• Food intolerance tests: what they really measure

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