What Is Causing a Mildew Smell in My Bathroom if I Have No Visible Signs of Mold?

You won't necessarily see evidence of mold in your home; mold is ubiquitous, and you may have hidden mold in damp areas, such as your bathroom. If you smell mildew in your bathroom, it may be behind wallpaper or drywall, underneath flooring or in the attic.

The Environmental Protection Agency (EPA) states that while locating hidden mold is difficult, cleaning what you can and reducing the humidity level in your bathroom will keep it under control.

Types of Mold

Countless types of mold exist. Mold thrives in damp, warm, dark conditions, and, while it can survive in dry air, it won't reproduce or grow. Common indoor molds include aspergillus, cladosporium and penicillium.

Dangers of Mold

Most mold is not highly toxic or dangerous, but many people are allergic or sensitive to mold spores. Typical symptoms include eye and skin irritation, nasal congestion and breathing difficulties. People with severe allergies or underlying respiratory conditions may have more severe reactions, such as fever and mold infections in the lungs. Molds affect people differently. Additionally, mold will eventually ruin and degrade a surface it grows on, making it an unwelcome hidden visitor in your home.

Hidden Mold Locations

Since mold grows best in warm, damp, moist places, it can be hidden under or behind almost any surface in your bathroom. If you smell a moldy or mildew odor and your bathroom is damp, you can safely assume you have mold growing behind the walls, under the floor or around leaking or sweating pipes and duct work. The EPA warns that uncovering mold by removing wallpaper, for instance, may cause a "massive release of spores" into your home. It suggests having a professional locate and remediate mold if the problem is severe.

Cleaning Mold

Add no more than 1 cup of bleach to 1 gallon of water to clean visible mold from hard surfaces, suggests the Center for Disease Control and Prevention (CDC). Wear skin and eye protection, open windows for ventilation and never mix bleach with other household cleaners because you can create toxic chlorine gas. Understand that completely removing mold spores is impossible, but once cleaned up, addressing the source of the moisture will prevent it from reproducing again.

Preventing Mold

Mold prevention involves tackling sources of excess moisture within your home. Repair or insulate roof leaks, sweating or leaking pipes and leaks around the tub and shower. Install fans or vents to expel humid air from the bathroom. Keep the humidity level in your home between 40 and 60 percent by using a dehumidifier in the bathroom or installing a whole-house dehumidifier if you live in a humid climate.