To cut costs, a high school modified its airconditioning system to increase its efficiency  The modified system, however, caused the humidity in the school air to decrease by 18 percent  Twenty-four hours after the decrease in air humidity, a 25 percent increase in the number of visits to the school nurse was reported
This shows that a decrease in humidity can make people ill
At least some of the visits to the school nurse after the system was modified were due to illness.