The majority of spider species that live outside your home and occasionally travel indoors are harmless to human beings and actually serve a beneficial purpose in natural habitats by eating the insect pests that are the most bothersome to people and plants. Still, many homeowners choose to err on the side of caution by repelling spiders from their homes before the spiders have an opportunity to enter. Many effective products and techniques are available for repelling spiders from your home.
Spiders prefer to live outdoors, where they have access to abundant food, moisture and protection. They will, however, travel indoors occasionally if a part of your home provides one of more of these things. The most effective ways of repelling spiders from your home is to reduce their opportunities for entry. Remove rocks, wood piles, compost piles, old boards, leaf debris and other spider habitation sites near the home. Using yellow or sodium vapor lights in lieu of standard white incandescent light bulbs for outdoor lighting will not attract insects that spiders prey on and will in turn not attract the spiders either. Use tight-fitting screens on all windows and seal all cracks and crevices with caulk to deny spiders entry.
The sanitation and exclusion methods described above are typically more effective when they are combined with a pesticide treatment. Contact insecticides can be sprayed directly onto observed spiders, but to repel spiders the long term requires a residual pesticide. Residual pesticides recommended for spider control typically include pyrethroid pesticide chemicals (bifenthrin, cyfluthrin, permethrin, tetramethrin and the like). Avoid total-release fogger insecticides as these will be largely ineffective at repelling spiders.
Always follow the manufacturer's printed application instructions in the first instance to ensure that the residual spider pesticide you use is most effective. Treat the areas of your home that are more likely to serve as spider habitats such as behind baseboards, in cracks and crevices, in and around boxes in attics and basements and similar areas. Monitor the treated areas regularly to check for a reduction in spider populations. Check for spider egg sacks in the areas you treat and vacuum up any you find as egg sacks will not be affected by residual insecticides.
It is important, in the interest of protecting the inhabitants of your home, to learn the characteristics of spiders that can potentially harm human beings and animals, such as black widow, brown recluse and hobo spiders. But with these exceptions, experts recommend tolerance of spiders whenever possible due to their ecological benefits. If spiders do reach nuisance or dangerous levels, however, and if none of the above steps succeed in repelling spiders from your home, consult a professional exterminator to repel spiders completely.