Adjust CPAP to Better Fit
A leaky mask can cause skin problems, and if you feel that your mask is lose or not adjusted to be right fit on your mouth, try to adjust its straps. There is a possibility that you are able to adjust the mask and the problem of itchy skin or irritation gets resolved. If you are not able to adjust the mask straps yourself you can seek help of another person.
Mask Size and Replacement
It can be a possibility that the size of the mask is not a right fit for you. So in that case get the mask replaced with one that fits to your size, and thus you can find a way to overcome your skin irritation problem. Also, there can be some problem with the straps, and not the mask. So get your mask inspected thoroughly again and replace it immediately whatever the problem is found with it.
Cleaning of Mask
It is most likely that you have been give a manual with the mask at the time you purchase it, so better read it thoroughly and perform routine cleaning of your mask regularly and as per instructions of the manufacturer. Using the mask without cleaning can also cause problem of the skin irritation. It is better to take care of the mask and place it at a clean and tidy place all the time.
See Doctor in Case of Infections
You should not wait further and see your doctor immediately if your skin has started developing serious infections. It is possible that you have fever, rashes and burning of the skin. In that case your doctor can recommend some effective solution for your skin.