This time of year in the wet Pacific NW becomes a verdant time indoors as well as outdoors. And that means more moisture in the house and mold growth.
Since we don't have a fan in our bathroom and rely on opening the window, we always have a problem of mold growth on the walls and ceiling where the steam likes to collect and hang out all day, even with the window wide open.
I've tried a number of desperate measures spreading from toxic (bleach) to inert (vinegar) with varying levels of success. So, let me give you a few suggestions of how to fight mold in your home.
Bleach solutions - This is probably the most effective way of getting rid of mold for longer periods of time. Unfortunately, the environmental impact of using bleach is high, you have to deal with the fumes and it's possibly dangerous (atomized droplets of bleach landing back on your face as you spray the ceiling, anyone?) and generally toxic.
Tea tree oil - Although tea tree oil is rather expensive, you are using only a small amount. This is probably your best bet for a natural solution, but the smell is strong and some people have issues with tea tree oil. Mix two teaspoons of tea tree oil in two cups of water and place into a spray bottle. Spray onto moldy areas - do not rinse. This mixture lasts forever.
White vinegar - Using straight up vinegar (don't even bother diluting it) can be effective in removing mold, but it takes a bit of work and doesn't last very long. The smell isn't so great, although it's much better than bleach, and can sting so be careful if you're doing ceiling spraying. I recommend applying directly with a sponge. That said, this is an inexpensive solution to your mold problems. Used straight up, vinegar purportedly kills 82% of mold. You can always try adding an essential oil like tea tree oil to boost the mold killing.
Grapefruit seed extract - The one nice thing about this mixture is that it is odorless and a little goes a long way. Mix 20 drops into two cups of water in a spray bottle and get to work. Many people have reported success with using this, although I haven't tried it.
Lemon juice - Apply full strength with a sponge. The smell by far is better than any other option listed here, but it's only moderately effective. So, if you are short on mold patience and hate redoing your lemon juice application frequently, you might try something else. Like the vinegar, it works for a short period of time.
Hydrogen peroxide - If you are dealing with mold on tiles, try using one part hydrogen peroxide with two parts water. Spray on and wait an hour.
Clove oil - Clove oil is anti-bacterial and anti-fungal and supposedly can help remove mold. Add several drops of clove oil (about half a dozen will do) to a half-filled bucket of water and apply with a sponge. Not all of the mold will be removed immediately. It may take a few days to work, and the surfaces should be dusted off after the mold looks dusty.
Concrobium mold control - This is an off-the-shelf product that contains mostly inorganic compounds that leaves behind an antimicrobial film upon drying that encapsulates fungus microbes and prevents growth. Supposedly, it's inert and the salespeople will drink it to prove how safe it is. This stuff works fairly well and lasts longer than the other options, but mold is mold and it always comes back.
Other options - It might be better to prevent mold in the first place by providing the right mix of ventilation and dryness. If your mold problems are in the bathroom, installing an exhaust fan should help. You may want to consider getting a dehumidifier if you really have a bad mold problem or using a space heater to heat and dry up trouble spots.