How is your immune function reflected in your smell and your face?

Writer: Justine Stanley
Editor: Madhumila Killamsetty
Artist: Lucie Gourmet

Studies have shown that people are more attracted to a certain individual’s body odour. In the “sweaty t-shirt” study lead by Claus Wedekind, men wear the same t-shirt for two days and women are asked to smell the t-shirts and rank them on sexual attractiveness.

In this study they found a correlation between women taking the pill and women not taking the pill and whether or not they were attracted to a person with opposite MHC genes. MHC genes are responsible for how foreign molecules from disease-causing organisms are presented to the immune system. This means that they play a key role in how efficiently and to which foreign molecules your body can react to. They also link to body odour which explains the potential attraction to a certain individual’s scent. It was found that women not on the pill were more attracted to men with opposite MHC genes to them. The same phenomena were observed when this experiment was conducted on mice initially. This makes sense because the more diverse your genes are, the better your chances are to fight off an infection. This is why you are attracted to the opposite MHC genes as it can maximise your range.

Later on, a study led by PabloSandro Carvalho Santos refuted this principle and concluded that we can at best state that MHC genes (or HLA in humans) influence body odour production or perception. They firstly did not find any correlation between women taking the pill and their attraction to the opposite MHC genes. They also found opposite data showing that women and men were more attracted to similar MHC genes. Therefore, concluding that human sexual attraction or mating preferences do not have any tangible proof to this day and new alternative studies with a broader view of different contexts would have to be led to support it and provide empirical proof. 

Lately,it has been established that your immune system could also be reflected in your face. A study published in the Royal Society suggests that “a relationship between facial attractiveness and immune function is likely to exist.” An examination of literature has led scientists to think that features such as clear skin, prominent cheekbones, bright eyes, and full, red lips have been deemed attractive throughout recorded human history in western civilization. But it was considered that this could be the result of beauty standards set by repeated western media exposure. Research also finds a consistent preference for symmetrical and average faces. Could this have something to do with the immune system’s activity?

In the study led by Mengelkoch and published in the Royal Society 79 women and 80 men from Texas Christian University were photographed and had blood taken to be sampled. They wore no makeup or jewellery and bore neutral expressions on their faces. They then recruited 492 more people to rate 25 randomly selected photographs. The results given were cross-checked with the blood analysis of the individuals. They examined the link between targets’ attractiveness and self reported health -measures of inflammation (in vivo), white blood cell count and in vitro tests of patients’ immune functions. This was done by looking at leukocyte proliferation in response to stimulants, phagocytosis of Eschericia coli, as well as NK cell counts and Staphylococcus aureus growth in plasma. It was found that people ranked with higher levels of attractiveness (i.e “This person is physically attractive”) had a higher count of phagocytes – the white blood cells that fight illness causing bacteria. Reciprocally, people with lower counts of attractiveness have fewer neutrophils which is an essential cell for phagocytosis.It was also found that the men ranked as more attractive had a greater NK cell cytotoxicity. This was not the case for women and it might be due to the fact  that high NK activity is linked with decreased oestrogen activity i.e., lower fertility and therefore higher chances of miscarriages too.

It has long been hypothesised that perceptions of attractiveness are a reflection of inclinations for traits historically linked to health and therefore maybe even immune function. It isn’t known yet whether it is due to specific facial features or whether an overall view of the person’s face  leads to a subconscious subjective evaluation of attractiveness. The research being led today proposes that attractiveness may provide insights into one’s immune function. But  similar to the hypothesis that links body odour and immune function or genes, there is no solid empirical proof suggesting that this can’t be refuted. Further, more detailed research would be needed to replicate and add precision to these results. Current research suggests that a relationship between facial attractiveness (although very tricky to measure due to its subjectivity) and immune function is likely to exist, but to what extent is still to be explored.

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