CPAP side effects are different from person to person. One of the most common CPAP side effect is discomfort caused by the mask itself. Individuals have reported “red marks” with their face or soreness on the bridge from their nose. It is generally due to the headgear straps being too tight. To make up for this particular side effect, many different masks are increasingly being developed. Additionally there are mask pads available or masks that only attach at the nostrils.