Put on the goggles and dust mask. Scrape all the peeling paint off the ceiling using a large putty knife. Hold a paint tray under the falling paint to contain the mess. Stand on a ladder that is securely positioned below your work area. Continue scraping until all the peeling paint is removed.
Sand the ceiling using 100-grit sandpaper to smooth rough spots. Spot sand if you only see a few rough spots, or sand the entire ceiling for even texture throughout.
Wash the ceiling with a mixture of 1 cup chlorine bleach in 1 gallon of water. Dampen a sponge in the cleaning solution, making sure to wring the sponge if it's too wet. Let the ceiling dry before proceeding.
Apply an adhesion primer to the ceiling using a sponge roller on an extension pole for the bulk of the ceiling. Use a bristle paintbrush to cut primer in and around the edges. Choose a primer/sealer for ceilings in high-humidity rooms, such as bathrooms. This prevents moisture problems that cause paint to peel, crack and mold. Allow the primer to cure according to manufacturer recommendations.
Paint the walls with a water-based paint that complements the primer. Apply it in the same manner as the primer. Use a sponge roller for the largest part of the ceiling and a paintbrush around the edges. Allow the paint to cure. Apply a second coat of paint.