Thinking about it - yes it's partly due to The Healthy House products. We have never used anything other than organic paints and varnishes and always use non toxic cleaning products. But it must also be down to the fact that we have never had a new sofa (often containing foam rubber, fire retardants and stain resistant treatments), don't have fitted carpet (often treated with insecticide and stain resistant treatments), and the curtains were made using fabric that the fire retardant washed out of. We run a dehumidifier in there and an Airfree which deals with any dampness and mould. The number of pollutants in modern furnishings, furniture, paints and cleaning products can seriously affect the contaminant levels in a room.
We think the allergy problem may be due to the fact that we once had a cat and since we treated the sofa and carpet with allergy sprays the symptoms are much improved.