A toddler with a runny nose every day of the year, eczema that won't quite settle, or recurrent night cough that gets blamed on "another bug" may have a household allergy. Unlike pollen, household allergens are around all year and concentrated in the place children spend most of their time — the bedroom. Identifying the trigger and getting both avoidance and proper symptom treatment in place often produces the kind of "she's a different child" change that catches parents by surprise. For a comprehensive overview, see our complete guide to child health. Healthbooq covers childhood allergies and common illnesses.
The Big Four Indoor Allergens
House dust mite (HDM). The single commonest indoor allergen worldwide. Microscopic arachnids that live in mattresses, pillows, duvets, soft toys, sofas, and carpets — anywhere with skin flakes (their food) and warmth and humidity (their preferred climate). The allergen isn't the mite itself but the protein in their faecal particles, which become airborne when bedding is moved and are inhaled or settle on skin. UK populations have particularly high HDM exposure because of soft furnishings, carpets, and central heating. Adnan Custovic and colleagues at Imperial College London have done much of the modern UK work on early-life sensitisation patterns.
Bedrooms are where exposure is highest, by a wide margin — children spend 10–12 hours a day there, with their face inches from the bedding.
Pet dander. Allergens come from saliva, dander (shed skin flakes), and urine — not the fur itself. So:
- No breed is genuinely hypoallergenic. Poodle crosses, hairless cats, and "low-shed" breeds still produce the proteins. They may be slightly less allergenic in some individuals, but they are not allergen-free.
- The main cat allergen (Fel d 1) is unusually small and sticky. It travels on clothes from cat-owning friends and persists in homes for months after a cat is rehomed.
- Dog allergens (Can f 1) behave similarly but are slightly less mobile.
A child with negative tests to dander but who reacts in pet-owning homes may be reacting to environmental allergens picked up by the pet, or to something else entirely.
Mould spores. Indoor damp produces Cladosporium, Alternaria, Penicillium, and Aspergillus spores. Mould allergy commonly causes rhinitis, can exacerbate asthma, and is particularly associated with damp housing — single-glazed windows with condensation, leaking pipes, untreated bathrooms, basements. UK housing stock has well-documented damp problems; this isn't rare.
Cockroach allergens. More common in urban areas, social housing, and high-density flats. Cockroach allergen in house dust is a recognised contributor to perennial rhinitis and asthma in some children, and is under-discussed in UK clinical practice. Worth raising with the GP if relevant.
A few less common but worth knowing: rodent allergens in some buildings, latex (rare in toddlers), and occasionally horse dander in stable-adjacent families.
How to Recognise It
The patterns that should make a parent or GP think household allergy:
- Year-round symptoms — runny nose, sneezing, blocked nose, itchy eyes — rather than the springtime-only pattern of pollen allergy.
- Symptoms that improve on holiday in a different environment and return on coming home. The "we went to Granny's for a week and his cough disappeared" story is classic.
- Symptoms worse in specific rooms — particularly bedrooms (HDM), or rooms with visible damp (mould), or homes with pets.
- Morning symptoms that ease as the day goes on — typical of HDM exposure, peaking from sleeping in a mite-rich bedroom and easing as the child moves into the rest of the house.
- Eczema that won't settle despite reasonable skin care.
- Recurrent night cough in a child without a cold, particularly with a parental history of asthma or eczema.
- Frequent ear or sinus infections in a child with persistent rhinitis — congestion blocks Eustachian tubes and predisposes to middle-ear problems.
The clinical picture (allergic rhinitis):
- Persistent clear nasal discharge
- Frequent sneezing, often in clusters
- Itchy nose, eyes, and the back of the throat
- Allergic shiners — dark rings under the eyes from chronic congestion
- An "allergic salute" — the upward palm-rub of the nose that wears a horizontal crease across the bridge
- Mouth breathing, snoring
- A pale or boggy lining inside the nose on examination
Asthma can coexist (the "atopic march" pattern: eczema → food allergy → allergic rhinitis → asthma is well described in early childhood). A child with bad year-round rhinitis is statistically more likely to develop or already have asthma.
Diagnosis
Skin prick testing is the standard first-line investigation in paediatric allergy. Tiny amounts of standardised allergen extract (HDM, cat, dog, mould mix, sometimes others) are introduced into the forearm with a small lancet. A raised wheal develops over 15 minutes; a wheal ≥3mm larger than the negative control is considered positive. Antihistamines need to be stopped for several days before the test, as they suppress the wheal response.
Specific IgE (sIgE) blood test measures the level of allergen-specific antibodies. Quantitative — useful when skin prick testing isn't available, when there's severe eczema preventing skin testing, or when antihistamines can't be stopped.
A few important caveats:
- Sensitisation is not the same as allergy. A positive test means the immune system recognises the allergen; clinical history determines whether it's actually causing symptoms.
- A negative test doesn't fully exclude allergy — context matters.
- Test panels with dozens of items done without clinical context produce noise. Targeted testing based on history is what's useful.
In the UK, NHS-funded testing is available via GP referral to paediatric allergy. Private testing varies in quality; reputable clinics use the same skin prick and sIgE methods.
Avoidance Measures
The evidence is best for dust mite avoidance when implemented properly and consistently. Patchy half-measures rarely work. The combination that has measurable effect:
- Allergen-impermeable encasings for mattress, pillow, and duvet. The widely-cited Cochrane reviews concluded inconsistent benefit because trial protocols often included only mattress covers; trials using full bed encasings consistently with weekly hot wash protocols have shown clinical improvement, particularly in children. Look for products certified to allergen-barrier standards.
- Weekly bedding wash at 60°C or above. Mites die at this temperature; warm-cool washes do not kill them. Pillowcases, sheets, mattress and duvet protectors all weekly. The duvet itself every 2–3 months.
- Soft toys — limit the number on the bed; freeze the favourites overnight in a sealed bag every couple of weeks (kills mites), then wash.
- Hard floors are easier than carpet in bedrooms. If carpet stays, vacuum with a HEPA-filter vacuum at least weekly.
- Reduce humidity below 50% — open windows, run extractor fans, dehumidifier in damp rooms. Mites need ambient humidity above ~55% to survive long-term.
- HEPA air purifier in the bedroom — modest but measurable effect.
For pets:
- Most effective: rehoming. Realistically, almost no family chooses this for an existing pet. Worth knowing for prospective additions to a sensitised household.
- Practical compromise: keep the pet out of the child's bedroom permanently. The bedroom is where most symptom production happens; protecting that space helps disproportionately.
- Wash the pet weekly (more for cats — twice weekly washing reduces airborne Fel d 1, though many cats object).
- HEPA filtration in living areas.
- Hard floors over carpet, machine-washable rugs.
For mould:
- Address the source — fix leaks, improve ventilation, repair damp walls. Cosmetic cleaning of visible mould without source control returns within weeks.
- Bathroom and kitchen extractor fans on during and after use.
- Open windows daily for ventilation, especially after showering and cooking.
- Dehumidifier in particularly damp rooms.
- Keep furniture slightly away from external walls to allow air movement.
For damp housing (UK rented sector particularly), tenants have rights — the Homes (Fitness for Human Habitation) Act 2018 and Awaab's Law strengthen requirements on landlords to address damp and mould affecting health.
Symptom Treatment
Avoidance helps, but rarely fully resolves symptoms in established sensitisation. Proper medication is part of management.
Non-sedating oral antihistamines. Cetirizine or loratadine at weight-appropriate doses, daily through symptomatic periods. Available over the counter from age 1 (cetirizine drops licensed from 12 months in some countries, 6 months in others).
Intranasal corticosteroid sprays. First-line for persistent moderate-to-severe allergic rhinitis in children. Mometasone (licensed from age 3) and fluticasone (from age 4) are well-tolerated; some are now available over the counter in the UK. They work over a couple of weeks of daily use rather than acutely; teaching the child to use them properly (head slightly forward, spray angled away from the septum) matters more than the brand.
Eye drops (sodium cromoglicate, olopatadine) for prominent eye symptoms.
Eczema management — emollients used liberally, topical steroids during flares, attention to bathing routines. Linked to but separate from environmental allergy management; the eczema doesn't always resolve when the rhinitis does.
Asthma — proper preventer therapy where applicable, reviewed regularly. A child with allergic rhinitis and asthma usually needs both treated; rhinitis treatment improves asthma control measurably.
Allergen immunotherapy (sublingual tablets for HDM specifically — Acarizax) is available from age 5 through specialist clinics. Three years of daily treatment can produce sustained tolerance in around two-thirds of suitable children.
When to Get a Specialist Opinion
Worth a paediatric allergy referral when:
- Symptoms are persistent and significantly affecting sleep or daily function despite reasonable medication
- Diagnosis is unclear after standard testing
- Multiple sensitisations make management complex
- Asthma is poorly controlled despite preventer therapy
- The family is considering immunotherapy
- A pet is a major potential trigger and decisions about household pet ownership need to be made
The summary worth holding: household allergy in a small child often goes undiagnosed for years, blamed on "constant colds" or "she just gets eczema." A targeted history, simple testing, and properly implemented avoidance plus medication can change a child's daily quality of life — and reduce the trajectory toward asthma — in ways the family didn't expect.
Key Takeaways
A toddler with a runny nose every day, eczema that won't settle, or asthma that flares in their bedroom may not be unlucky — they may be sensitised to something living in the house. The big four indoor allergens are house dust mite, pet dander, mould spores, and (in some homes) cockroach. The clinical signature is symptoms that are year-round rather than seasonal, that improve on holiday and worsen on return, or that are worse in specific rooms. Diagnosis is clinical history plus either skin prick testing or specific IgE blood test. Management combines targeted avoidance — for dust mite the evidence supports impermeable bedding covers used with weekly 60°C bedding washes — and proper symptom treatment with non-sedating antihistamines, intranasal corticosteroid sprays for persistent rhinitis, and proper eczema management. Sublingual immunotherapy for dust mite is available from age 5 in specialist clinics.
