When I was growing up, I vividly remember that my older sister Shannon was always getting sick. It seemed that she would have to take time off of school at least once a month because she was too sick to go in. Her immune system was just not as good as it should have been, and the more often she got sick, the worse it got.
I hated seeing her like that. When I got home from school I wanted to be able to play with my older sister, but instead she would be covered in blankets, sneezing and blowing her nose. It would sometimes take a few days before she felt well enough to play with me, and I didn't know what I could do to make her better.
My mother was obviously concerned that Shannon was such a sickly child, so she did some research on immune system health. She had us take lots of vitamin C, and made sure that we ate healthily all the time. But the best tip she found was that keeping a room at between 30 and 60 percent humidity is ideal for the immune system.
She put a humidifier in my sister's room and turned it on while she was sleeping. We could tell it made a difference right away. My sister stopped getting sick as frequently, and her immune system continued to get stronger until she barely had to miss school at all.
Now even though she is an adult, Shannon has a humidifier in her house. She sleeps with it on and it helps to keep her healthy, especially when the air is naturally drier than it usually is.