It generally doesn't cure the cold completely, but it certainly reduces the intensity.
I'm not completely sure why it works, but it does. Most likely there are some sort of antibiotic properties within the chemical makeup of the garlic.
I don't argue though. As long as it keeps working. My wife swears by it.
Were you talking about birth control or cold control?
An easier way to take it is to put the crushed clove on a piece of toast. I always doubted the power of garlic until I came down with a cold I couldn't kick. It was amazing how fast I recovered. Just make sure that glass of water is ready.
We use it chopped and swallowed as a mosquito/bug repellent, and put it in our dogs food for the same reason. It really works. It does smell up your sweat a tad though.
Many years ago there were reports that the compound known as allicin in garlic was effective against both bacteria and viruses.