It is universally accepted that smoking has many serious health and life hazards among which is lung cancer. These hazards affect not only the smoker, but those around him or her as well.
The Shari`ah has stressed the importance of being in good health to the extent that Prophet Muhammad (peace be upon him) even advised Muslims in all ages to strike a balance between eating and drinking, so as to evade any harmful effects on the health.
Smoking did not exist in the time of the Prophet (peace be upon him), but our great religion of Islam has laid down general principles from which many laws have been derived.
In the Qur’an, Almighty Allah says, “Be not cast by your own hands to ruin, and do good. Lo! Allah loves the beneficent.” (Al-Baqarah 2:195)
In another verse, Almighty Allah says, “And do not kill yourselves.” (An-Nisaa’ 4:29)
The Prophet (peace be upon him) is reported to have said, “Whoever drinks poison, thereby killing himself, will sip this poison forever in Hellfire.” (Al-Bukhari and Muslim)
You do not have to repeat your wudu after smoking, but you should remove the offensive odor from your mouth with something that can take it away.
Almighty Allah knows best.