Why do fleas bite some people and not others? - briefly
Fleas are attracted to individuals who emit higher levels of carbon dioxide, body heat, and specific skin chemicals such as certain fatty acids and lactic acid, which vary between people. Genetic factors like blood type and immune response also influence susceptibility, causing some hosts to be bitten more frequently than others.
Why do fleas bite some people and not others? - in detail
Fleas are attracted to cues that vary among individuals, and these cues determine whether a person becomes a target. The primary factors are:
- Body temperature – higher skin temperature releases more heat, signaling a favorable blood source.
- Carbon dioxide output – people who breathe more heavily or have a larger metabolic rate emit greater CO₂ levels, which fleas detect as an indicator of host presence.
- Skin chemistry – sweat contains lactic acid, urea, and fatty acids; the concentration and composition differ with genetics, diet, and hormonal status, creating distinct odor profiles.
- Blood type – studies show that certain blood groups, particularly type O, produce surface antigens that fleas find more appealing.
- Microbial flora – the skin’s bacterial community metabolizes secretions into volatile compounds; variations in microbial populations influence attractiveness.
- Movement and vibration – active individuals generate more mechanical disturbances, drawing flea attention.
These biological signals interact with flea sensory systems. Fleas possess thermoreceptors, CO₂ chemoreceptors, and olfactory receptors tuned to specific volatile organic compounds. When a combination of strong cues is present, fleas are more likely to land, probe, and feed. Conversely, individuals with lower heat emission, reduced CO₂ output, or skin chemistry that lacks attractive metabolites experience fewer bites.
Environmental and behavioral elements modify exposure. Wearing loose clothing may create a barrier, while tight fabrics increase skin contact. Regular grooming removes flea eggs and larvae, reducing local infestations. Use of insect repellents containing DEET, permethrin, or essential oils interferes with flea chemoreception, lowering bite incidence regardless of personal physiological traits.
In summary, differential biting results from a complex interplay of host physiology, skin biochemistry, and flea sensory mechanisms, amplified by personal habits and preventive measures.