Remove mold from bathroom caulking by applying undiluted lemon juice with an old toothbrush, scrubbing gently to prevent damaging the caulking and leaving the juice on the caulking for an hour before rinsing it. The acidity of the juice kills the mold and bleaches the caulk to help remove stains, according to SFGate. Before you begin the process, put on a face mask so you do not breathe in the mold spores.
If lemon juice is not available, other options for cleaning the mold include undiluted white vinegar or 1/4 cup of 3 percent hydrogen peroxide diluted with 1/2 cup of water. Once you remove the mold, prevent it from growing again by providing proper ventilation. After each shower or bath, leave the exhaust fan running or open a window or door so the moisture evaporates. Mold spores do not grow in dry conditions.
If the mold has been growing for a long time, it may be growing around the caulking. The best solution in this case is to remove the old caulking and replace it with new. After removing the old caulk, treat the area with one of these solutions to kill any mold spores. If the area you are caulking is small, use a tube of bathroom caulk that you apply by squeezing the tube. For larger jobs, it is more economical to buy caulking in tubes that require an inexpensive caulking gun to squeeze the caulk out.