The answer is the bed bug injects an anesthetic as it feeds.
Bed bugs are tiny blood sucking insects that have an exoskeleton. These insects are found in places like the edges of the bed, cavities, etc. where they hide in the day time. During night, these insects come out and bite their hosts to feed on the blood. However like Dr. Logan, no one feels the pain due to the bite because the bed bugs also inject an anesthetic to avoid the host from detecting their presence. Anesthetic is a drug substance that stops the pain receptors from signalling the brain about the pain.