What rises above 60% relative humidity
- Dust mites: they need humidity above about 50% to survive and multiply fastest above 60%. Their droppings are the main year-round indoor allergen.
- Mould spores: growth starts on surfaces above about 60% and speeds up above 70%.
What the evidence says
- The WHO guidelines on indoor dampness and mould (2009) conclude that people in damp or mouldy homes have more respiratory symptoms, infections and asthma attacks.
- UAE residents describe the same list: waking "choking and with puffy eyes", sneezing and itchy eyes indoors, new allergy diagnoses after a mouldy summer (Khaleej Times and The National reports).
- General information, not medical advice. See a doctor about symptoms.
Who is most affected
- Children and infants.
- People with asthma, allergic rhinitis or eczema.
- Anyone with a weakened immune system or an autoimmune condition.
- Anyone sleeping in a sealed bedroom where humidity climbs at night as the AC cycles off.
What helps
- Hold indoor humidity at 45–55% all year; mites and mould both decline there.
- Filter the air: fine particle filtration removes spores, mite fragments and dust.
- A ducted dehumidifier with integrated filtration does both from the ceiling void, for every room at once.
