Black Spots on the Walls After Spraying for Bed Bugs

Bed bugs suck the blood of warm-blooded animals during the night. After they have a nocturnal blood meal, they digest the substance and eliminate it. The bug's defecation can leave behind small black, red or brown spots on walls, along baseboards, mattresses or other home surfaces. A large infestation of the pests can leave behind considerable staining. Even after successfully spraying for the pests and eliminating them, the homeowner will still have to clean up the unsightly fecal spots.

Painting may be required to cover bed bug staining.

Wall Damage

After consuming a nocturnal blood meal, the bed bug usually scampers off to congregate with its brethren during the daylight hours. The bugs often gather along baseboards, on the wall behind headboards, around electrical receptacles, under wall paper or along the base of the wall beside the floor. Even after the live bed bugs have been killed, the bug's skin casings, dead eggs and fecal stains will remain. The areas of the wall with fecal staining often secrete a sweet, musty odor. Bed bug fecal staining on walls will often require cleaning and repair work to remove the unsightly spots after the bugs have been successfully eliminated.

Cleaning Stains

Vacuum up all the bed bug casings and eggs. Promptly dispose of the vacuum cleaner bag. Wipe the wall down with warm, soapy water to try to remove the staining or use a mild detergent. Lift the edges of wall paper to peek beneath it to see if staining appears on the wall's surface. Cracks in the wall's plaster may also have staining. Clean out the cracks and repair them. Look along the wall's crown molding for any staining. Remove wall pictures to see if any staining exists on the wall behind them.

Wall Repair

Remove damaged or heavily stained wall paper. Clean up the fecal residue beneath old wall paper with warm, soapy water. Make sure all fecal staining has been successfully removed before hanging new wall paper. Clean up all stains on painted walls before repainting so the blood does not seep through the new paint. Caulk all cracks along molding and wall baseboard to prevent any future bed bugs from crawling into such locations.


The U.S. Environmental Protection Agency recognizes more than 300 pesticide spray products for the treatment of bed bugs. Always follow the directions on the pesticide's label when applying to control bed bugs, or have a professional pest service. Spot spray treatments, know as residual insecticides, usually work best if the wall crevices and cracks have been thoroughly cleaned of eggs, dirt, insect casings and fecal blood prior to spraying, according to the Ohio State University Extension.