A recent study published in Evolutionary Psychology found that immunization led to an increase in perceived body odor attractiveness and a decrease in facial attractiveness.
Social species, including humans, have evolved sophisticated mechanisms to detect and avoid contagious others, effectively mitigating the spread of infectious diseases within their communities. This ability to discern others’ health status is critical due to the inherent risks posed by high population densities and frequent social interactions. Researchers have identified various perceptual cues—ranging from visual signals to olfactory cues—that social species utilize to identify and stay clear of ill others.
This phenomenon extends beyond mate selection and encompasses a broad range of social interactions, highlighting its significance in preventing the spread of disease. Notably, the capacity for early detection of health threats relies on the accurate interpretation of a variety of signals, as proposed by the contagion indicator hypothesis, which suggests that certain traits can serve as reliable indicators of an individual’s health status and pathogen resistance.
Empirical studies across species have established the role of these cues in social and mating contexts. For example, female mice exhibit a marked preference for the scent of healthy males over those carrying parasites, a pattern echoed in findings related to humans’ responses to the body odor of healthy versus infected individuals. Research has also found that visual and vocal cues are integral to the assessment of health status. Changes in skin coloration, vocal characteristics, and even the production of certain sounds have been linked to an individual’s current health.
This work included 21 healthy, non-smoking Czech men aged 18 to 40 who had not been vaccinated against hepatitis A/B or meningococcus in the past decade. Participants provided body odor samples, facial photographs, and voice recordings before and 14 days after vaccination, when antibody response was expected to be highest. he vaccination was against hepatitis A/B and meningococcus using Menveo and Twinrix Adult vaccines, administered intramuscularly.
Body odor was collected using cotton pads and t-shirts after participants adhered to a strict regimen to avoid influencing odor quality, with samples stored at -20°C to prevent microbial activity alterations. Facial photographs were taken under standardized conditions, and voice recordings were made using a professional setup to ensure consistency. Blood samples were collected to assess specific antibodies, CRP levels, and steroid hormones before and after vaccination to study immunological responses.
A total of 88 Czech women provided ratings, focusing on odor, facial attractiveness, and vocal appeal. Facial skin color was measured using spectrophotometry and image analysis, and ratings of facial attractiveness and healthiness were conducted in controlled environments to emulate natural interaction distances.
Dagmar Schwambergová and colleagues found a significant positive correlation between odor attractiveness and healthiness before and after vaccination. Odor intensity was inversely related to attractiveness and healthiness ratings, suggesting that stronger body odors were perceived as less appealing and healthy. For facial and vocal characteristics, prevaccination and postvaccination ratings were significantly correlated, highlighting stability in these perceptions over time. However, no significant correlations were observed between the attractiveness of body odor and facial or vocal attractiveness, either before or after vaccination.
Regarding changes in perception post-vaccination, there was a noticeable increase in body odor attractiveness and a decrease in odor intensity, suggesting an improved perception of body odor quality post-vaccination. Conversely, facial attractiveness and healthiness ratings declined after vaccination, indicating a perceived decrease in these qualities. Vocal attractiveness showed no significant change post-vaccination. Further, no significant changes were observed in facial coloration (lightness, redness, yellowness) after vaccination, nor did skin color significantly affect perceptions of facial attractiveness or healthiness post-vaccination.
Body height was positively correlated with body odor attractiveness and vocal attractiveness in both conditions, while body weight was negatively correlated with postvaccination facial healthiness. CRP levels were associated with body odor attractiveness and intensity before vaccination but not after, and similarly, CRP levels predicted facial attractiveness before vaccination but had no significant relationship with postvaccination facial attractiveness or healthiness, nor with vocal attractiveness in either condition.
A limitation noted by the authors is the small sample size, exacerbated by difficulties in recruitment due to vaccine hesitancy and strict inclusion criteria, which may affect the study’s generalizability and statistical power.
Overall, these findings suggest that humans utilize multiple sensory cues in health assessments, supporting the “multiple messages” hypothesis, indicating that different modalities convey distinct information about an individual’s health status.
The study, “Immunoactivation Affects Perceived Body Odor and Facial but Not Vocal Attractiveness”, was authored by Dagmar Schwambergová, Žaneta Pátková, Jitka Třebická Fialová, Vít Třebický, David Stella and Jan Havlíček.