So on average I smoke about once every two weeks. I noticed that usually the day after smoking I feel sniffles and a cold coming coming on. If I smoke a lot, it is virtually guranteed to happen the next day, even if I am feeling completely healthy. The few times I have smoked when I had colds, I have woken up feeling much sicker the next day. So does anyone else think that thc might lower your immune system. I mean its not like it happens every time. For example, during the summer it will rarely happen. However, during the winter I am almost afraid to smoke cause I hate having a cold.