Though thinking that you're safe from spiders while you sleep would be nice, there's almost nowhere in your home a spider won't go. Despite this, not uncommonly one will live in your bed. You can decrease the possibility of this happening by taking simple measures to make your bed less appealing.
A commonly-cited statistic states that the average person swallows eight spiders per year, presumably in his sleep. Snopes.com busts this myth, attributing it to a 1954 book about insects. According to the University of Washington, a spider might enter your bed twice per year, further detracting from this myth.
Spiders are different from other bed critters, such as fleas and bedbugs, in the sense that they don't usually bite. While other bugs may bite you for their own nourishment, a spider is most likely to bite to defend itself. So, if you wake up with a mysterious bite, it doesn't mean you have spiders in your bed. If a spider has been in your bed, it's probably the only one. The Bugs in My Bed website states that spiders are solitary bugs.
Spiders typically get onto a bed using another object. For instance, if your sheets hang off your bed, a spider could use them to climb up from the floor. Avoid allowing the sheets to hang, as well as placing objects on your bed which have been on the floor, such as moving boxes or furniture. This should be enough to keep spiders off your bed.
Unpleasant though they may be, spiders serve an important purpose in your home: They kill other bugs. Since they aren't likely to crawl onto your bed, you probably don't need to treat your bed to kill them.