"The "Sick Period" is a stage when cigars have a distinct ammonia smell and even a nasty taste in most cases. This is the time when tobacco is fermenting and releasing ammonia. Normally, this stage lasts a fairly short time, but it will vary depending on the age and fermentation length of the tobacco used in the cigar. This smell/taste will go away as the tobacco is aged and the ammonia is allowed to be ventilated away from the tobacco.
Most commonly, this stage is most noticeable in Cuban cigars. It will generally run from few months to a year depending on the individual cigar.
This stage usually does not exist with most non-Cuban premium cigars as most non-Cuban manufacturers will age their tobacco considerably longer before rolling it and even then will often store the rolled cigars for an extended period before shipping them."