Our LG Split airconditioner gives COMMON COLD when ...

Our LG split air conditioner gives COMMON COLD when we sleep with temperature 26 but not 29?

Answer: It may be strange or even new to you. But this is not for the first time. Whenever we sleep, the temperature in the split air-conditioner is fixed at 26, we get COMMON COLD, including running nose. But i tried keeping the temperature at 28 or 29 and I noticed that  we are well.