Sneezing and a runny nose indoors that will not stop. What actually works against house dust?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
It is not pollen season, yet you sneeze when you get home and wake with a blocked nose. In Japan, the second most common cause of allergic rhinitis after pollen is "house dust", and most of that is the droppings and dead bodies of house dust mites (hyōhi-dani). Before you buy an air purifier, here is the order in which the measures work.
The measures, their effect and their priority
| Priority | Measure | Details | Effect |
|---|---|---|---|
| 1 | Bedding | Vacuum futons, mattresses and pillows at least once a week (20 seconds per m², slowly). Wash sheets and covers weekly (at 55°C (131°F) or above the mites die too; an ordinary wash still rinses away the allergen). Anti-mite covers (a high-density weave that mites cannot pass) | Large |
| 2 | Floors | Remove carpets and rugs, or switch to washable ones. Wipe tatami and wooden floors (vacuuming alone stirs dust up). Use a vacuum with a HEPA filter and weak exhaust | Large |
| 3 | Humidity | Indoor humidity 50–60% or below (mites multiply most at 60–80% and 20–30°C). Dehumidifier, ventilation, the air-conditioner's dry mode. Closets and oshiire (built-in futon cupboards) too | Medium to large |
| 4 | Fewer fabrics | Fabric sofa → leather or synthetic leather, only soft toys that can be washed (wash and tumble-dry, or bag them and freeze for a day → wash), heavy curtains → washable ones | Medium |
| 5 | Air purifier | Reduces airborne allergen. Guide: HEPA filter, rated floor area twice the size of the room | Small to medium (not enough on its own) |
| 6 | Mite traps and anti-mite sprays | Supplementary. Reduce live mites, but not the allergen (droppings and bodies) | Small |
- Mite basics: house dust mites (chiri-dani) are 0.3 mm long, invisible to the eye, and do not bite. They feed on human skin flakes and dander, and a single futon can hold tens of thousands to hundreds of thousands. The allergen is the droppings and dead bodies, which remain after the mites die — so the focus is on "removing and washing away" rather than "killing".
- Sun-drying alone is not enough: the inside of a futon rarely reaches 50°C, and droppings and bodies remain after airing. Vacuum after airing — the two go together.
- Cleaning order and timing: in the morning before people move about, or right after coming home. High places → low places, wipe → vacuum (vacuuming first stirs dust up). Open the windows while cleaning; people with allergies should wear a mask.
- Pets: dog and cat dander is also a major allergen. Keep them out of the bedroom; brush once a week (outdoors).
- Medicines and therapy: antihistamines (over-the-counter and prescription), steroid nasal sprays (prescription; highly effective, with little effect on the rest of the body). Sublingual immunotherapy (covered by health insurance for mites since 2015, age 5 and over) involves placing a tablet under the tongue every day; many people find their symptoms much milder after 3–5 years. Few people know that an option addressing the root cause exists.
- Testing: a blood test (specific IgE) can check the major allergens — mites, pollen, pets, mould — all together (covered by health insurance). Knowing "what you react to" cuts wasted effort.
- Children: mite control in infancy is generally described as relevant to preventing the onset of asthma, and bedding measures are given particular weight.
[Verify] Check the breeding conditions for mites, mite numbers in bedding, and the start year and minimum age for health-insurance coverage of sublingual immunotherapy against Japanese Society of Allergology and MHLW materials.
Misunderstanding 1｜Buy an air purifier and the problem is solved
Most allergen has settled on floors and bedding; an air purifier alone has limited effect. Bedding and floors come first.
Misunderstanding 2｜Sun-dry the futon and the mites die
The inside rarely reaches 50°C, and even when mites die, the droppings and bodies remain as allergen. Vacuum after airing; wash the covers.
Misunderstanding 3｜Kill the mites with traps or sprays and the symptoms go
Fewer live mites, but the allergen (droppings and bodies) remains. Removing and washing is the core.
Misunderstanding 4｜The only option for house dust allergy is to keep it down with medicines
Sublingual immunotherapy (covered by health insurance) aims to change the underlying reaction. It takes 3–5 years, but many people find their symptoms much milder.
Misunderstanding 5｜The more you vacuum the better
The exhaust stirs dust up, so wipe first, vacuum slowly, and pair it with ventilation and a mask. Method matters more than frequency.
---
Sources
- Japanese Society of Allergology, "Practical Guideline for the Management of Allergic Rhinitis in Japan, 2024 edition" [アレルギー性鼻炎診療ガイドライン（鼻アレルギー診療ガイドライン2024年版）]
https://www.jsaweb.jp/
- Ministry of Health, Labour and Welfare (MHLW), "Allergy Portal (mite control)" [アレルギー疾患対策：アレルギーポータル（ダニ対策）]
https://allergyportal.jp/
- Tokyo Metropolitan Institute of Public Health, "Indoor mites and allergy" [室内のダニとアレルギー]
https://www.tmiph.metro.tokyo.lg.jp/
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
About this article
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.
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