Why do bedbugs bite some people but not others?

Understanding Bed Bug Bites

The Nature of Bed Bug Feeding

How Bed Bugs Find Hosts

Bed bugs locate potential hosts through a combination of sensory cues that guide them from hiding places to exposed skin.

Chemoreception allows detection of carbon dioxide emitted by breathing. The insects possess specialized sensilla on their antennae that respond to rising CO₂ concentrations, triggering movement toward the source.

Thermoreception enables identification of body heat. Infrared-sensitive receptors on the legs and antennae register temperature gradients, directing bugs toward warm areas of a sleeping surface.

Vibrational perception helps locate a moving host. Bed bugs sense minute disturbances in the fabric of mattresses or bedding caused by shifting bodies, prompting them to climb upward.

Tactile cues finalize contact. Once within a few centimeters, the bugs use their tarsi to feel for skin texture and pressure, confirming a suitable feeding site.

The sequence of host‑finding steps can be summarized:

Detect elevated CO₂ levels.
Follow thermal gradient toward heat.
Respond to mechanical vibrations from host movement.
Use tactile feedback to locate skin and initiate feeding.

These mechanisms operate continuously, allowing bed bugs to exploit human hosts while remaining concealed during periods of inactivity.

The Role of Chemical Cues

Bedbugs locate hosts primarily through volatile chemicals released from the human body. Carbon dioxide, emitted in each breath, creates a gradient that guides insects toward a potential source. Once within a few meters, the insects rely on skin‑derived odorants—primarily fatty acids, lactic acid, and ammonia—to pinpoint a feeding site. These compounds vary markedly among individuals, influencing the likelihood of detection.

Variations in personal chemical profiles stem from several factors:

Sweat composition, which differs with genetics, diet, and hormonal status.
Skin microbiota, which metabolize secretions into distinct volatile molecules.
Use of personal care products that either mask or amplify odorants.

When a person's odor blend aligns with the sensory preferences of bedbugs, the insects exhibit increased attraction and subsequent biting. Conversely, individuals whose chemical emissions fall outside the optimal range experience fewer or no bites. The selective response to these cues explains the uneven biting pattern observed across a population.

Factors Influencing Bed Bug Attraction

Human Body Chemistry

Carbon Dioxide Emissions

Carbon dioxide emissions from a human host constitute the primary chemical signal that attracts bedbugs. Individual metabolic rates determine the volume of CO₂ exhaled per minute; higher rates produce stronger plumes that can be detected at greater distances. Consequently, people with elevated respiration—due to fever, stress, or physical activity—are more likely to be located and bitten.

Ambient CO₂ concentrations also influence bedbug foraging. Laboratory experiments show that increasing background CO₂ from 400 ppm to 1,000 ppm reduces the gradient between host and environment, diminishing the insects’ ability to discern specific hosts. In settings with poor ventilation, accumulated human‑generated CO₂ can mask individual differences, leading to more uniform biting patterns.

The relationship between CO₂ output and selective biting can be summarized:

Metabolic output: higher resting or induced respiration → stronger CO₂ plume → increased attraction.
Environmental background: elevated ambient CO₂ → weaker host‑specific gradient → reduced selectivity.
Ventilation quality: adequate airflow maintains distinct plumes; stagnant air blends emissions, altering host detection.

Understanding these dynamics assists in developing control strategies, such as improving indoor air exchange to disperse CO₂ plumes and reduce the likelihood that bedbugs locate particular individuals.

Body Heat and Sweat

Bedbugs locate potential hosts by detecting heat emitted from the body surface. Individuals with higher peripheral temperature create a stronger thermal gradient, which speeds up the insect’s approach. Elevated skin temperature also shortens the time required for the bug to confirm a feeding site, increasing the likelihood of a bite.

Sweat provides chemical signals that guide bedbugs toward a host. Human perspiration contains compounds such as lactic acid, ammonia, and fatty acids; these act as kairomones that stimulate the insect’s sensory organs. The concentration and composition of these substances vary with genetics, diet, stress level, and ambient humidity, creating distinct olfactory profiles among people. Bedbugs preferentially respond to profiles that contain higher levels of attractant molecules, resulting in selective feeding.

Key points linking thermal and sudoriferous cues to bite variability:

Higher skin temperature → stronger thermal cue → faster host detection.
Greater sweat production → increased release of kairomones → enhanced attraction.
Individual differences in sweat chemistry → selective response by the insect.
Environmental factors (e.g., room temperature, humidity) modulate both heat dissipation and sweat evaporation, indirectly affecting bite risk.

Understanding these physiological determinants clarifies why some individuals experience frequent bites while others remain largely untouched.

Skin Compounds and Pheromones

Bedbugs locate potential hosts by detecting heat, carbon dioxide, and a range of chemical signals emitted from human skin. Among these signals, the specific composition of skin secretions and the pheromonal cues they generate determine the degree of attraction for individual insects.

Key skin-derived compounds that influence bedbug behavior include:

Lactic acid, produced by sweat glands, creates a volatile gradient that many hematophagous insects follow.
Ammonia, a by‑product of bacterial metabolism on the skin surface, enhances olfactory detection.
Fatty acids such as isovaleric and caproic acid, released from sebaceous glands, contribute to a distinctive odor profile.
Volatile organic compounds (VOCs) generated by the skin microbiome, including short‑chain aldehydes and ketones, vary between people and affect host preference.

Bedbugs also emit aggregation pheromones that interact with host odors. When a bedbug encounters a person whose skin emissions match the chemical signature of its pheromone blend, the insect is more likely to initiate feeding. Conversely, individuals whose skin chemistry diverges from this blend experience fewer bites.

Variability in skin chemistry arises from genetic factors, diet, hygiene practices, and microbial community composition. These differences alter the concentration and ratio of the compounds listed above, producing a spectrum of attractiveness that explains why some people receive frequent bites while others remain largely untouched.

Individual Variability in Reactions

Immune Response and Histamine Production

Bedbug feeding success depends largely on the host’s immune reaction to the insect’s saliva. When a bedbug pierces the skin, it injects anticoagulants and anesthetic proteins that trigger a localized immune response. The body’s mast cells release histamine, a vasoactive amine that expands blood vessels and creates the characteristic swelling and itching. Individuals who generate a strong histamine surge experience pronounced welts, which may attract additional bites because the inflamed area is more accessible to the insect’s probing mouthparts.

Variability in histamine release stems from several physiological factors:

Genetic polymorphisms affecting FcεRI receptors and histamine‑metabolizing enzymes (e.g., HNMT) alter the magnitude and duration of the response.
Baseline IgE levels influence mast cell sensitivity; higher IgE predisposes to rapid degranulation upon exposure to bedbug salivary antigens.
Skin microbiome composition can modulate immune signaling pathways, either amplifying or dampening histamine production.
Previous sensitization to bedbug saliva or cross‑reactive allergens primes the immune system, resulting in quicker and larger histamine releases on subsequent encounters.

Conversely, people with lower IgE concentrations, efficient histamine degradation, or a skin environment that suppresses mast cell activation may exhibit minimal or no visible reaction, allowing bedbugs to feed unnoticed. Understanding these immunological differences clarifies why some hosts attract frequent bites while others remain largely untouched.

Perception of Bites and Itch Threshold

Bedbug bites trigger a localized immune response that varies among individuals. The intensity of this response depends on the quantity and activity of salivary proteins introduced during feeding, which can differ from one host to another. When the immune system recognizes these proteins, it releases histamine and other mediators that produce redness, swelling, and itching. Some people mount a strong histamine response, resulting in noticeable lesions; others exhibit a muted reaction that may go unnoticed.

Perception of the bite is further shaped by the sensory threshold for itch. This threshold reflects the minimum level of nerve activation required to generate the conscious sensation of pruritus. Factors influencing the threshold include:

Genetic variations in histamine receptor density
Prior exposure to bedbug saliva, which can desensitize or sensitize cutaneous nerves
Skin condition such as dryness or barrier integrity
Psychological state, with stress capable of lowering the itch threshold

When the itch threshold is low, even minor inflammatory signals produce a pronounced urge to scratch, making the bite apparent. Conversely, a high threshold can mask the same level of inflammation, allowing the bite to remain undetected. Consequently, the combination of immune reactivity and individual itch sensitivity explains why some hosts experience conspicuous bites while others do not.

Psychological Factors and Awareness

Psychological state influences the likelihood of being bitten. People who are anxious or stressed often exhibit increased skin temperature and perspiration, creating cues that attract bedbugs. Heightened vigilance can also lead to frequent scratching, which releases odorants that bedbugs detect.

Awareness of bedbug presence modifies exposure risk. Individuals who regularly inspect bedding, use protective encasements, and maintain clutter‑free environments reduce opportunities for insects to locate a host. Conversely, lack of knowledge about bedbug behavior—such as their preference for dark, undisturbed zones—results in complacent habits that facilitate attacks.

Key psychological and awareness‑related factors:

Stress‑induced physiological changes – elevated cortisol, skin conductance, and subtle scent alterations.
Perceived threat level – low concern leads to delayed detection and longer feeding periods.
Behavioral routines – nightly inspection, prompt laundering of infested fabrics, and avoidance of sleeping on the floor.
Education – understanding bedbug hiding spots and feeding patterns improves preventive measures.

In summary, mental stress amplifies bodily signals that attract bedbugs, while informed, proactive habits diminish contact opportunities. Both dimensions interact to explain why some persons experience bites while others do not.

Misconceptions and Alternative Explanations

The Myth of «Sweet Blood»

Bedbugs do not select hosts based on a notion that certain people have “sweet” blood. The belief stems from anecdotal observations and a misinterpretation of the insects’ sensory mechanisms. Scientific investigations reveal that attraction relies on measurable physiological cues rather than the composition of blood sugars.

Key determinants of host preference include:

Carbon dioxide output – higher metabolic rates generate more CO₂, creating a stronger plume that guides bedbugs toward a potential host.
Body temperature – warm skin surfaces emit infrared radiation, which bedbugs detect with specialized receptors.
Skin volatiles – compounds such as lactic acid, ammonia, and specific fatty acids vary among individuals and influence attraction.
Blood type and secretions – research shows modest correlations between certain blood groups and bite frequency, but no evidence links glucose concentration to increased appeal.

Experimental data consistently demonstrate that bedbugs respond to the combined gradient of these cues. When CO₂, heat, and skin chemicals are presented together, the insects exhibit rapid orientation and feeding behavior. Isolated glucose solutions, even at elevated concentrations, fail to elicit a comparable response.

Consequently, the “sweet blood” myth lacks empirical support. Bedbug bites result from a complex interplay of metabolic and chemical signals, not from the sweetness of the host’s blood.

Other Pests and Skin Conditions

Bedbugs are not the only arthropods that cause cutaneous reactions; fleas, ticks, mites, and lice also produce lesions that can be mistaken for bedbug bites. Each organism delivers saliva or other irritants that trigger immune responses varying among individuals. The presence or absence of a visible reaction often reflects the host’s immune sensitivity rather than the pest’s feeding behavior.

Common pests and their typical skin manifestations include:

Fleas – small, red papules surrounded by a halo; frequently appear on lower legs and ankles.
Ticks – enlarging, erythematous nodules at the attachment site; may develop a central necrotic core.
Mites (e.g., scabies, chiggers) – linear or serpentine tracks of intense itching; burrows or erythematous papules are characteristic.
Lice – pruritic papules near the scalp or body hair; secondary excoriations are common.

Skin conditions that mimic insect bites also influence perceived susceptibility:

Allergic contact dermatitis – localized redness and swelling after exposure to allergens such as detergents or metals.
Atopic dermatitis – chronic, itchy eczematous patches that can be exacerbated by scratching.
Urticaria – transient wheals appearing suddenly, often triggered by temperature changes or stress.

Differential diagnosis relies on lesion distribution, size, and temporal pattern. Bedbug bites typically appear in clusters or linear rows on exposed skin, whereas flea bites concentrate on the lower extremities, and tick bites remain solitary. Recognizing these distinctions prevents misattribution of symptoms to bedbugs when other pests or dermatologic disorders are responsible.

Environmental Factors Affecting Bite Visibility

Environmental conditions shape how readily bed‑bug bites are seen. Temperature, humidity, and ventilation alter skin reactions and the insects’ feeding behavior, creating differences in the appearance of lesions.

High temperature accelerates blood flow, intensifying swelling and redness.
Low humidity dries skin, reducing inflammatory response and making marks faint.
Poor ventilation raises carbon‑dioxide levels, prompting longer feeding periods that increase bite prominence.
Sunlight exposure before or after feeding triggers pigment changes, either highlighting or masking lesions.
Bedding fabrics that retain heat (e.g., polyester) amplify skin irritation, whereas breathable materials (e.g., cotton) lessen visible swelling.
Residual soaps or lotions modify skin pH, influencing the immune response and the contrast of bite marks.

These factors interact with individual physiology, leading to observable variation in bite visibility across different settings.

Strategies for Detection and Prevention

Recognizing the Signs of Infestation

Bedbug infestations often go unnoticed because only a fraction of occupants develop visible bites. Detecting an outbreak relies on observing additional indicators that appear before or alongside skin reactions.

Small, rust‑colored spots on sheets or mattress fabric; these are digested blood excretions left by the insects.
Dark, pepper‑like specks on walls, furniture, or bedding; these are fecal deposits that accumulate over weeks.
Tiny, translucent shells measuring 2–3 mm; they are exuviae shed after each molt.
Live insects, measuring 4–5 mm, flattened and reddish‑brown, found in seams, creases, or hidden cracks.
A faint, sweet, musty odor detectable in heavily infested rooms; the scent originates from the bugs’ defensive chemicals.

Bite patterns alone cannot confirm an infestation, as some individuals experience no reaction due to immune tolerance or skin sensitivity. Regular inspection of the listed signs, especially in seams, headboards, and upholstered furniture, provides reliable evidence of a colony’s presence and enables prompt control measures.

Professional Pest Control Measures

Professional pest control directly influences the frequency of bedbug bites by reducing the insect population to levels where human contact becomes rare. Effective control begins with a thorough inspection that identifies all harborages, including seams of mattresses, baseboards, and furniture crevices. Inspectors often use magnification, flashlights, and trained detection dogs to locate hidden insects and eggs.

Key interventions employed by licensed technicians include:

Chemical application – targeted use of regulated insecticides such as pyrethroids, neonicotinoids, or desiccant dusts. Products are applied to cracks, seams, and voids where bedbugs hide, following label directions to maximize efficacy and minimize resistance.
Heat treatment – raising ambient temperature to 45‑50 °C for a minimum of four hours. Heat penetrates fabrics and structural voids, killing all life stages without chemicals.
Steam treatment – focused steam at 100 °C applied to mattresses, upholstery, and wall voids. Steam destroys eggs and nymphs on contact.
Encasement – installing zippered mattress and box‑spring covers rated to contain bedbugs. Encasements prevent re‑infestation and simplify monitoring.
Monitoring devices – placement of interceptors under legs of beds and furniture. Devices capture moving insects, providing data on treatment success.

Integrated pest management (IPM) combines these tactics with scheduled follow‑up inspections, documentation of findings, and client education on sanitation and clutter reduction. IPM protocols require repeated treatments spaced 7‑14 days apart to address newly emerged nymphs before they mature.

When professionals execute IPM consistently, the overall bedbug load declines sharply, resulting in fewer bites for occupants who previously experienced none. The reduction in exposure explains why some individuals stop being bitten after a comprehensive treatment program, while untreated environments maintain high bite incidence.

Personal Protective Actions

Personal habits influence the probability of being bitten by bedbugs. Skin temperature, carbon‑dioxide output, and body odor vary with activity level, diet, and hygiene, creating detectable cues for the insects. Adjusting these cues reduces attraction.

Maintain a regular bathing schedule with unscented soap to limit odor compounds that attract bugs.
Keep body temperature stable by avoiding excessive heat exposure before bedtime; lower skin warmth diminishes feeding signals.
Reduce carbon‑dioxide emission by limiting alcohol and caffeine intake in the evening, as metabolic rates drop and exhaled gas volume decreases.
Wear tightly woven, light‑colored pajamas; dense fabrics hinder probing mouthparts, and lighter colors provide fewer visual contrasts.
Apply insect‑repellent formulations containing DEET or picaridin to exposed skin; these chemicals interfere with chemosensory receptors.

These measures target the physiological signals bedbugs use to locate hosts. Consistent implementation lowers the likelihood of detection and subsequent feeding, contributing to personal protection against bites.