A proverb says:
"The treated cold lasts seven days and the untreated cold lasts a week".
A pharmaceutical company however claims in a PR article that its product containing Oxymetazoline will reduce average duration of a runny nose to four days, and that oxymetazoline has a proven antiviral effects:
shortened runny nose treatment ... about one third ... patients were treated only for four days, instead of six days for those using Saline.
proved beyond any doubt antiviral effect of oxymetazoline
The PR article mentions a study by Dr. Stephan Kölsch from Merck Selbstmedikation GmbH, Darmstadt from September 2005, with no further references.