R.R.
Basically takes about 7-10 days for my little guy to get over a cold completely.
My nephew was always sick when younger, what my sister thought were colds were viral infections for the most part, he just seemed more vulnerable to getting them, whereas some people are just carriers. He also has allergies and went on Zyrtec before a year old because of a constantly running (yellow and green at times) nose..
One thing his ped pointed out was that my sister was too clean. She told her to let him get dirty and not use all the antibacterial stuff so much, that she was causing him to be sick. He always took vitamins, ate well (he's a picky eater now that he's 10) got enough rest, etc., but after my sister eased off he actually got sick less.
Hope he feels better soon.