Grandma used to say - if you ignore a cold it will last 7 days, if you treat it it will go in week.
When I lived in Bristol, I briefly had a GP called Dr. Mendel (no, not a nazi) who was into homeopathy. When I moved to a different part of Bristol, I changed GP, and the new one was much more down to earth. I went to see him when I had a really bad cold that just wouldn't go away, and he gave me some sensible advice about wrapping up warm and keeping hydrated and so on. In those days, GPs tended to dish out prescriptions like sweets just to lull you into a false sense of "being cured", but this one was very sensible and didn't.
I said to him "oh, so I don't need to take anything?" to which he scratched his beard, looked at me thoughtfully and said "well, I suppose you COULD try massive doses of Vitamin E, or whatever other fad Dr. Mendel happens to be into at the moment, but you'll get better whether you do or whether you don't, and it's a lot cheaper if you don't."