We have moved (ok moving) house. The tenants before us had a cat(s) and since being here, DD3 who is 6 months has awful watery eyes and runny nose.

Stupid question... Is there anything I can give her?
Best to consult a doctor as DD3 is only 6 months.. But neighbor's cat might be the cause of DD3 watery eyes and runny nose, she might be allergic to danders. check the ventilation of your house as well and the dusts. Hope DD3 gets well..