Mushrooms may add color and variety to an outdoor garden or lawn, but mushrooms that sprout up in your bathroom are a cause for concern. Bathrooms provide mushrooms with ideal growing conditions. Even though many mushrooms are harmless on their own, the presence of mushrooms in your bathroom is indicative of much more significant moisture problem that may lead to more serious mold infestations.
The fungal spores that generate mushrooms are microscopic and light enough to be carried by even small gusts of wind. Spores are present on clothing, window screens and plants, but two of the single-cell spores must combine in order to begin mushroom growth. Since mushrooms require high humidity and low-light, oftentimes the conditions inside your home don't support mushroom growth, but bathrooms are particularly well-suited for sprouting mushrooms. High heat, excess moisture and low-lighting provide the conditions that allow mushrooms to flourish in bathroom floors, walls or even ceilings, particularly around areas where moisture collects or pools.
Though the threat of poisonous mushrooms may be the first concern you consider, the mushrooms themselves are unlikely to pose a serious threat to your health. A majority of mushrooms are harmless, though you should not eat any mushrooms that grow in your bathroom as a matter of caution. Bathroom mushrooms are a sign of a significant moisture problem in your bathroom that could support more harmful growth of black mold or mildew. Mold and mildew flourish in the same conditions that support mushroom growth, and exposure to mold poses a risk of serious allergic reactions or respiratory illnesses according to the Federal Emergency Management Agency.
Initial removal of large mushrooms is as simply as donning a pair of rubber gloves and picking the offending fungi out of the floor, wall or ceiling. Once you remove the largest parts of the mushrooms, copper- or neem oil-based fungicides are an effective treatment for killing the remaining structures of the mushrooms. Using fungicides indoors requires proper ventilation as well as eye and mouth protection. If you prefer to not use fungicides, a diluted solution of bleach and water is also an effective means for killing mushrooms. Full eradication may require several applications of either a fungicide or a bleach solution.
Treating existing mushrooms in your bathroom with a fungicide is not enough to prevent future fungal problems in your bathroom. If the levels of humidity in your bathroom are high enough to support mushrooms, they are also high enough to support the growth of toxic mold or structural damage to underlying wood structures in your bathroom. Ensure that your bathroom is fitted with a ventilation fan to remove humidity from the room. Wet towels also provide a breeding ground for mold and mushrooms, so hang towels to dry or transfer them immediately to a washing machine. If the seals around your toilet or bathtub are leaking or pooling water, have them repaired by a professional contractor. If your water damage problem is severe, you may need to replace flooring or walls with new, dry wood.