Our LG Split airconditioner gives COMMON COLD when ...

Our LG Split airconditioner gives COMMON COLD when we sleep with temperature 26 but not 29?

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