Bed bugs are small, nocturnal parasites that require blood meals to grow and reproduce. These pests are roughly the size of an apple seed and hide in mattress seams, furniture, and cracks during the day, emerging only when a host is inactive. The common experience of one person being bitten more frequently than another often raises the popular question of whether bed bugs prefer one sex over the other. Examining the scientific evidence behind host-seeking behaviors determines if bed bugs actively discriminate between male and female hosts.
How Bed Bugs Locate a Host
Bed bugs rely on environmental cues rather than sight to locate a host, as they are most active at night when a host is asleep. The primary long-range attractant they detect is carbon dioxide (CO2), which is exhaled during respiration. This gaseous plume can be detected from several meters away and serves as the initial signal that activates host-seeking behavior.
Once they are within close proximity, approximately 3 feet, other cues guide them to the specific feeding site. These short-range signals include body heat and various volatile chemical compounds emitted from the skin. While CO2 and host odors draw the bug toward the general area, the final approach is governed by the host’s heat signature, which is detectable only at a distance of a few centimeters.
Research on Sex-Specific Attraction
Scientific studies comparing bed bug attraction rates between human males and females do not support a significant preference based solely on sex. The insects are opportunistic feeders motivated by the presence of blood and the physical cues of a resting host. One large survey found that more women reported visible skin reactions compared to men, but this difference was not statistically significant in determining who was bitten more often.
The theory that bed bugs prefer females due to differences in pheromones or skin hairiness remains unproven in controlled laboratory settings. Bed bugs are highly attuned to the fundamental signals of mammalian life, not gender-specific traits. When tested with human breath, male and female bed bugs demonstrated similar orientation behavior toward the odor source.
Factors Driving Differential Biting Rates
The appearance of differential biting rates in a shared environment is explained by individual physiological and immunological variations among people. A significant factor is a person’s metabolic rate, which directly influences the amount of CO2 and heat they emit. Individuals with a higher metabolism, such as pregnant women or those who naturally run warmer, may release more of these primary attractants, making them a more appealing target.
Differences in skin chemistry also play a role, as bed bugs are attracted to specific volatile organic compounds and lactic acid produced by the skin’s unique bacterial microbiome. Subtle variations in diet, lifestyle, and even blood type can alter the host’s chemical signature; some limited studies suggest a minor preference for Type O.
The most common reason one person seems to be bitten more is the variability in the human immune response to the bug’s saliva. The bed bug injects an anticoagulant and an anesthetic when feeding, and the visible bite reaction is an allergic response to these proteins. Approximately 30% of people show little to no visible skin reaction to the bites, even when fed upon, leading to the false impression that they were not bitten at all. The person who reacts strongly experiences noticeable welts and itching, creating the perception that they are the primary target, even if the exposure was equal.