Making homes more energy efficient has led to an increase in “indoor pollution”, medics have warned.
Experts said that attempts to better insulate homes and cut out drafts could be risking the health of children, by exposing them to excess pollutants.
The report, from the Royal College of Paediatrics and Child Health (RCPCH) and the Royal College of Physicians, warns of increasing evidence linking indoor air pollution to asthma, wheezing, conjunctivitis, dermatitis, and eczema.
Its authors said making homes “more airtight” had brought new risks to their inhabitants - especially to children, who are most vulnerable because their lungs are still developing.
The authors said that, while buildings of modern houses have prioritised insulation and energy efficiency, ventilation provision and advice has not kept up.
The colleges called on councils to introduce free indoor air testing for residents.
And they said midwives,care workers and social workers should be asked to give advice on clean air during visits.
Professor Jonathan Grigg, paediatric respiratory consultant from the RCPCH, said: "We're finally paying attention to the quality of our outdoor air and this is long overdue.
"It's harder to get population level data on the quality of indoor air, but the evidence in this report paints a worrying picture.
"Children in the UK spend most of their time indoors, with just 68 minutes spent outside on an average day.
"Too many of our homes and schools are damp and poorly ventilated - this is adversely affecting the health of children."
They said air quality was being put at risk by a range of indoor pollutants, including paints, varnishes, waxes, cleaning sprays and flame retardant-treated furnishings.
Professor Stephen Holgate, special adviser for the Royal College of Physicians, added: "If we ask our children to spend their childhood days in unhealthy spaces, then we're storing up problems for future health."
The report says: "Homes are ... becoming more airtight, to reduce thermal losses and improve energy efficiency.
"Energy efficiency is important to reduce our use of fossil fuels and to prevent climate change, but without adequate ventilation it could inadvertently worsen indoor air quality and impact health.
"There must be performance-based design of buildings that prioritises solutions which improve energy efficiency, protect the health and well-being of people inside, and reduce carbon emissions."
The report warns that little is known about how different pollutants react in combination, and that the secondary pollution created when they mix can be more harmful than the original pollutants.
Air quality tends to be poorer in low quality housing, where ventilation may be inadequate or insufficient, the authors said.
Some families with young children with severe allergies or respiratory issues have been left to crowd-fund for air purifiers and dehumidifiers, they added.
Opening windows would improve ventilation but would mean heat loss and increased heating bills, and security concerns, the report says. And it says those living in polluted areas may want to keep fumes out of their homes.