Quoting Leisurely Duchess:" It's really funny that I had no clue that quitting smoking is what made me sick. I had no nicotine withdrawals ... [snip!] ... it], which loosens up all the crap including bacteria and viruses caught in your sinuses and lungs which can make you very ill"
Actually.. stopping smoking would re-moisten your mucus membranes which would/could in turn cause coughing, sneezing and/or runny nose.... there are microbes in your lungs, that are part of your residential flora.. which do not harm you.. that would be coughed up if you happen to be carrying a microbe that is not part of your normal flora, and is harmful - re-mositening your mucous membranes would be beneficial because coughing, sneezing, and runny nose are removing the microbes from your body.. it is the best thing that could happen. If they remained dried out, like a smokers.. it would be easier for the non-residental, harmful microbe to colonize and cause infection.
The nausea/vomiting is from withdraw of nicotine and/or other chemicals inside of the cigarettes.
So anyway.... quitting may make you nauseous/vomit.. which may not feel great... but it is only temporary..
. but the flu-like symptoms are very beneficial and are your body's natural response to remove harmful bacterium.. that is hindered when you are a smoker
Therefore, the sooner you quit the better.