Year-Round Allergies: Dust Mites, Pets and Mould
When “hay fever” never stops. Reading the pattern to work out the trigger, an honest look at what avoidance achieves, and why a spray beats a tablet here.
Part of the Complete Hay Fever Guide.
Key fact: If your hay fever does not stop in autumn, it probably is not hay fever. Year-round allergic rhinitis is usually house dust mite, a pet or mould — and the pattern of when you are worst is what tells you which.
Seasonal or year-round
Allergic rhinitis is the same condition whatever sets it off: an allergic reaction in the lining of the nose producing sneezing, itching, a runny nose and blockage. What differs is the trigger, and triggers divide into those that come and go with the seasons and those that are present all the time.
The distinction matters for two practical reasons. First, year-round allergens produce a different symptom mix — blockage tends to dominate over sneezing and itching, because the lining never gets a chance to recover. Second, treatment has to be year-round too, and the mainstay shifts from antihistamine tablets to a steroid nasal spray, because blockage is what a spray treats and a tablet does not.
| Seasonal (hay fever) | Year-round (perennial) | |
|---|---|---|
| Trigger | Tree, grass or weed pollen; fungal spores | House dust mite, pets, indoor mould |
| Timing | Predictable months, worse outdoors and in dry breezy weather | All year, often worst indoors and on waking |
| Dominant symptom | Sneezing, itching, streaming | Blockage, mouth breathing, reduced smell |
| Eyes | Usually prominent | Often much less so |
| Mainstay | Antihistamine plus a spray through the season | A steroid nasal spray used continuously |
Reading the pattern
You can get a long way without any testing simply by noticing when you are worst.
| When you are worst | Points towards |
|---|---|
| On waking, easing through the morning; worse in bed and when making the bed | House dust mite |
| Within minutes of entering a particular home, or on contact with a specific animal | Pet allergen |
| In damp rooms, in autumn, around compost, leaf litter or houseplants | Mould |
| When cleaning, vacuuming or disturbing soft furnishings | Dust mite, or animal allergen in the fabric |
| On temperature change, strong smells, alcohol or spicy food — and with no itch | Non-allergic rhinitis |
| Always the same side, constantly, regardless of setting | Something structural — worth examining |
House dust mite
House dust mites are microscopic arachnids that live in bedding, mattresses, upholstery and carpet, feeding on shed human skin. The allergen is not the mite itself but the protein in its faecal pellets, which become airborne when bedding and furnishings are disturbed. They need humidity to survive, which is why they thrive in bedrooms and in poorly ventilated homes.
The characteristic story is being worst on waking and for the first hour or two of the day, because the sleeper spends eight hours with their face in the largest reservoir in the house.
An honest word about avoidance. Individual dust mite measures — a mattress cover on its own, or a HEPA vacuum on its own — have repeatedly failed to show meaningful symptom benefit in trials. Intensive combined measures sustained over time do better, but they are demanding. For most people, medication does considerably more than housekeeping, and it is worth knowing that before spending several hundred pounds on bedding.
If you want to try, the measures with the most logic behind them are allergen-impermeable covers on mattress, duvet and pillows; washing bedding weekly at 60°C, which kills mites rather than merely rinsing allergen away; keeping indoor humidity down through ventilation; removing carpet, heavy curtains and surplus soft toys from the bedroom; and vacuuming with a HEPA filter while someone with the allergy is out of the room.
Pets
The allergen in cat and dog allergy is carried in dander, saliva and urine rather than in hair, which has two consequences people find surprising.
- “Hypoallergenic” breeds are not. A low-shedding coat means less hair on the sofa, not less allergen. Studies comparing allergen levels in homes with supposedly hypoallergenic dogs have found no consistent difference.
- Cat allergen is exceptionally persistent and sticky. It attaches to clothing and travels, which is why people react in houses that have never had a cat, and why levels remain high for months after a cat has left a home.
- Keeping the animal out of the bedroom is the single highest-yield measure short of rehoming, because it protects the eight hours of heaviest exposure.
- Washing the animal reduces allergen briefly, but levels return within a couple of days, so it needs to be frequent to matter.
Rehoming a pet is a decision few people are willing to make and it is not usually necessary. Bedroom exclusion, thorough cleaning, hard flooring where possible and proper medical treatment will control symptoms for most people.
Mould
Mould allergy comes in two forms. Outdoor spores from Alternaria and Cladosporium peak in late summer and autumn, particularly around compost, cut grass and fallen leaves, and are a common explanation for someone who believes they have a very long hay fever season. Indoor moulds grow wherever there is persistent damp: bathrooms, kitchens, window reveals, behind furniture on cold external walls, and in the soil of overwatered houseplants.
Indoor mould is the one worth acting on, because unlike dust mites it can usually be removed. Fix the source of the damp rather than repeatedly cleaning the surface: ventilate when showering and cooking, deal with condensation on cold walls, use extractor fans, and address any leak. Cleaning mould off a wall that is still wet simply resets the clock.
When it is not an allergy at all
A substantial number of people with a permanently blocked, running nose have no allergy at all, and this is the usual explanation for antihistamines doing nothing whatsoever. The distinguishing feature is that non-allergic rhinitis does not itch — itching is the signature of an allergic reaction, and its absence points firmly away from one.
The triggers are things like temperature change, strong smells, alcohol and spicy food rather than anything you could be tested for, and the treatment differs accordingly. We cover it, along with the other reasons a nose stays blocked when allergy treatment has not helped, in a blocked nose that will not clear.
Treating year-round rhinitis
The principles are the same as for hay fever, with one shift of emphasis. Because blockage dominates, the steroid nasal spray is the mainstay rather than the addition, and it needs to be continuous rather than seasonal. Give it a fortnight of daily use with correct technique before judging it — the other reasons a nose stays blocked are covered in a blocked nose that will not clear.
A daily non-drowsy antihistamine is added where there is genuine itching, sneezing or eye involvement. Saline rinses are a useful and underrated adjunct for crusting and thick mucus. Decongestant sprays have almost no role here, because the exposure never ends and the seven-day limit makes them unusable as a long-term answer.
Is allergy testing worth it
Sometimes, but less often than people expect. Skin prick testing and specific IgE blood tests identify what you are sensitised to — but sensitisation is common and does not always mean that allergen is causing your symptoms. A positive result changes nothing if the treatment would be the same either way.
Testing earns its place when a specific answer would change a real decision: whether to take on or rehome an animal, whether to invest heavily in dust mite measures, whether occupational exposure is responsible, or whether someone with severe symptoms failing full treatment is a candidate for immunotherapy. For a straightforward blocked nose that responds to a spray, it adds cost and no benefit.
Frequently Asked Questions
Why do I have hay fever symptoms all year round?
Because the trigger is probably not pollen. Year-round allergic rhinitis is usually caused by house dust mite, a pet or indoor mould, all of which are present continuously. The timing tells you which: worst on waking points to dust mite, worse on contact with an animal or in a particular home points to pet allergen, and worse in damp rooms or in autumn points to mould. Blockage tends to dominate rather than sneezing.
Do dust mite covers and special vacuums actually work?
Individual measures have generally failed to show meaningful symptom benefit in trials, and that includes mattress covers used alone and HEPA vacuuming used alone. Intensive combined measures sustained over a long period do better, but they demand real effort. For most people medication achieves more than housekeeping, which is worth knowing before spending heavily on specialist bedding.
Are hypoallergenic dog and cat breeds really better for allergies?
No. The allergen is in dander, saliva and urine rather than hair, so a low-shedding coat means less hair around the house but not less allergen. Studies comparing homes with supposedly hypoallergenic dogs have not found consistently lower allergen levels. Keeping the animal out of the bedroom is a far more effective measure than choosing a breed.
Why don't antihistamines help my blocked nose?
Because nasal blockage is caused by swelling of the lining driven by inflammation, not by histamine. Antihistamines treat sneezing, itching and a runny nose well and do very little for congestion. A steroid nasal spray used every day is the most effective treatment for blockage. If you have no itching at all, it is also worth considering non-allergic rhinitis, which antihistamines do not help.
Should I get an allergy test?
Only if the answer would change what you do. Testing identifies what you are sensitised to, but sensitisation is common and does not always mean that allergen is causing your symptoms. It is worth doing when a specific answer would drive a real decision — about a pet, about major changes at home, about an occupational exposure, or about whether immunotherapy is appropriate. For symptoms that respond to a nasal spray, it adds cost without changing treatment.
References
- NHS. Hay fever. nhs.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Allergic rhinitis. cks.nice.org.uk
- British Society for Allergy & Clinical Immunology. BSACI guideline for the diagnosis and management of allergic and non-allergic rhinitis. bsaci.org
- Joint Formulary Committee. British National Formulary: antihistamines, allergen immunotherapy and allergic emergencies. bnf.nice.org.uk
- electronic Medicines Compendium. Summaries of Product Characteristics. medicines.org.uk
- Met Office. Pollen forecast and the UK pollen calendar. metoffice.gov.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Allergy medicines differ in how much drowsiness they cause and in who can take them, and decongestant nasal sprays are not for long-term use. If you have asthma, breathing symptoms that worsen alongside hay fever need review rather than more antihistamine. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.