ok, i think too many of you are too quick to bash the op. I don't think he means something magical to cure your cold.
But for example, there's ingredients like antihistamines that dry out your sinuses. That's called a cover up. To make you feel better.
But to fight the cold, you really want a decongestant. It will make your life a little worse in the sense that your nose will be a water faucet and you will need to blow it a lot, but you will get chunks and chunks of mucus/phlegm.
You really gotta look at what dayquil does. It's similar to Tylenol cold which I believe gives you a little phenylephrine to help with your cold. In a sense it helps you decongest a little, but they're not that effective.
Here, let's look at Tylenol
Ingredients
Active Ingredient: Acetaminophen (Symptom reliever)
Purpose: Pain reliever/fever reducer
Active Ingredient: Dextromethorphan HBr (Symptom reliever)
Purpose: Cough suppressant
Active Ingredient: Guaifenesin (Helps you fight cold symptoms)
Purpose: Expectorant
Active Ingredient: Phenylephrine HCl (Helps you fight cold symptoms)
Purpose: Nasal decongestant
So basically 2/4 ingredients help suppress your symptoms. It helps you feel better, but it's the latter 2 you need to help fight it. Of course you do want a cough suppressant because you don't want to cough every 30 seconds at the office if you're sick.
If you really want to fight your cold, I would highly recommend mucinex. That stuff just throws guaifenesin at you which loosens up mucus and if you have a huge sinus, get the "D" version which throws in pseudoephedrine, the stuff that really works and clears your mucus. If you notice the main ingredients in mucinex it's just heavy does guaifenesin and some cough supressant. If you get the nasal version, it's got pseudoephedrine too, so yeah. The main purpose is to help you get the crap out of your body. I don't believe any of this really fights the cold, but there's some ingredients that just cover up your symptoms, while others allow you to fight off those symptoms (in a certain sense).
Of course to really help your body heal, you need more than this. Vitamin C, zinc and echinacea help.