Toilet seats get moldy fast if they aren't cleaned frequently or properly. This often happens on the underside (the bowl side) of the seat, no matter what the toilet seat is made of (porcelain, acrylic or wood). Soft toilet seats may also develop mold around the edges, where moisture collects in the seams. You should keep your toilet seat clean to prevent mold, which is both unsightly and unsanitary. Remember: Taking steps to prevent mold takes less time than removing the mold once it has grown.
Open you bathroom door for ventilation (and a window too, if possible). Put on rubber gloves and protective eyewear--bathroom cleaners for mold and mildew can be caustic. Avoid getting it on your skin or in your eyes.
Lift the seat and its lid up to clean the underside of the seat first. Apply a bathroom cleaner containing bleach to the underside (the bowl side) of the seat. Use a cleaner that squirts on, for easiest application. Leave the cleaner on for several minutes (check the label to see if it indicates a period of time it should be left on the surface; if it doesn't give a specific amount of time, leave it on for 10 to 15 minutes).
Dip your toilet brush in the toilet water. Scrub the mold and mildew present on the underside of the toilet seat and the hinges that hold the seat on. If the toilet brush isn't sufficient for removing the stains, use a synthetic scrubbing sponge.
Rinse off the inner side of the lid with a damp, disposable cloth. Put the seat down and rinse out your sponge. Apply a few drops of the bleach bathroom cleaner on the sponge. Apply this to the seat and leave it on for 10 to 15 minutes.
Scrub the seat with the sponge until mildew, mold and other stains are gone. Repeat this procedure on both sides at least once a week to keep mold or mildew from forming on and around your toilet seat.