The findings come from researchers including Carl-Gustaf Bornehag of the Swedish National Testing and Research Institute in Boras, Sweden. The report appears in the October issue of the journal Environmental Health Perspectives.
Affected children had at least two incidents of eczema (an allergy-related skin condition), wheezing related to asthma, or hay fever symptoms (runny nose without a cold) in the past year. At the study's end, they had at least two of three possible symptoms.
Researchers took dust samples from the moulding and shelves in the children's bedrooms.
PVC flooring in the children's bedrooms was also associated with symptoms.
Phthalates are commonly added to plastics as softeners and solvents. They're used in a wide variety of products including nail polish and other cosmetics, dyes, PVC vinyl tile, carpet tiles, artificial leather, and certain adhesives.
By leaching out of products, phthalates have become "global pollutants," say the researchers. More than 3.5 million metric tons of phthalates are produced annually.
Phthalates aren't new, but they have become more common in recent decades. Towards the end of World War II, only "very low levels" of phthalates were produced.
In fact, phthalates are now so widespread that they are hard to avoid.
Asthma and allergies have also increased in the developed world during the last 30 years, prompting some experts to wonder if environmental changes are responsible, since genetic shifts might not be seen as quickly.
This study concentrated on three common phthalates: BBzP, DEHP, and di-n-butyl phthalate.
BBzP was associated with rhinitis and eczema and DEHP was linked to asthma; di-n-butyl phthalate was not associated with any symptoms.
The dust samples didn't have outlandish concentrations of the phthalates. Levels fell within the range of what is normally found in indoor environments, say the researchers.
"Given the phthalate exposures of children worldwide, the results from this study of Swedish children have global implications," they conclude.