Air conditioner. And cough for babies. ?

AC helps to cool the environment, and also reduce humidity , which aids in feeling comfortable. As long as one is breathing through the nose, it doesn't matter. However if the nose is blocked due to allergy or viral infection, and the nose is unable to warm or humidify air going to the lungs , the child can develop cough because of dry , cold air going to the lungs . Also air is not filtered by the nose, so there is higher chance of getting infection, specially if there are other people in the same enclosed space having an infection.