A Blog by Ed Yong

Photos of sneezing can put our immune systems on red alert

NHS_posterTake a look at this poster. British people will probably be familiar with it already. For everyone else, it was released last year by our National Health Service when fears of a flu pandemic were at their height. When we see images of diseases and their symptoms, we typically feel disgust and repulsion. But unbeknownst to us, our immune systems have started reacting too.

In a small but compelling study, Mark Schaller from the University of British Columbia found that people who see images of sneezes and other signs of disease mount a stronger immune response to later infections than people who see unrelated images. This is the first evidence that the mere sight of a possible infection, even through a photograph, can set our bodies’ defences on high alert.

Previously, Schaller has suggested that the visual signs of disease trigger a variety of psychological tics that reduce our chances of infection. A disgusted reaction fulfils this role by making us less likely to approach potential sources of contagion. Last year, another group showed that a sneezing passer-by can make people more worried about completely unrelated threats, like heart attacks, crime and accidents. To Schaller, these reactions are all part of our “behavioural immune system” – our means of preventing infections by changing our behaviour.

But his latest study suggests that images of sickness can prime our actual immune systems too. He recruited 28 volunteers, split them into two groups, and showed them two slide shows. The first slides were just shots of furniture. The second set showed either signs of infectious diseases, such as pox, skin lesions or sneezing, or images of people brandishing guns, mostly aimed directly at the viewers.

Schaller collected blood samples from the volunteers before and after each slide show, and mixed them with molecules that give away the presence of marauding bacteria. He wanted to see how strongly the white cells in the blood would respond to these danger signs. To do that, he measured the concentrations of a protein called interleukin-6 (IL-6), which while blood cells secrete in response to infections, burns or wounds. The more IL-6 there is, the stronger the body’s immune reaction.

He found that the white blood cells responded much more aggressively to the bacterial molecules after the volunteers saw the symptom slides. The furniture images didn’t change the amount of IL-6 in the recruits’ blood samples, the gun images raised these levels by 7%, but the disease images increased them by 24%.

Guns_diseaseThis suggests that the immune system reacts with extra vigour after its owner sees an image specifically related to disease, rather than one that invokes a general sense of threat or danger. Indeed, when questioned later, both groups reported the same levels of stress and fear even though only one of them manifested an actual physical reaction.

There is one caveat – the people who saw the gun images had higher levels of IL-6 in their blood samples before the experiment than those who saw the disease images. The difference wasn’t statistically significant, but it could suggest that Schaller didn’t split his groups randomly enough. He acknowledges this possibility but he says that the two groups weren’t any different in terms of their personality traits or how worried they were about disease. Nonetheless, this is an issue that could easily be addressed by doing a larger follow-up study using more volunteers.

For the moment, the effect is certainly plausible. From an evolutionary point of view, putting our immune systems on alert if we see signs of infection might reduce the odds of contracting a disease without having to distance ourselves from our social groups. However, Schaller suggests that in modern times, such responses might be counterproductive. An image of a sneeze is clearly not a sign that disease is imminent, and priming our immune systems to a non-existent threat isn’t the best use of our valuable energy.

Reference: Psychological Science http://dx.doi.org/10.1177/0956797610368064

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14 thoughts on “Photos of sneezing can put our immune systems on red alert

  1. A ‘counterproductive’ response? This seems like an odd conclusion to me. I’d be very interested to see whether talking about an illness causes the same immune response as seeing an image, because we get an enormous amount of our information about the world from other people. For example, you’re much more likely to see an image of a sneeze during flu season; it’s unlikely to be completely irrelevant! The number of people we interact or share space with is much greater than we can adequately visually observe for signs of illness, and whatever information we can eke out from others is likely useful as well.

    Even if the response to an image is extremely transient and lasts on the order of a few minutes, the ad is on the subway. Or elsewhere in public, surrounded by people; you know, where you would see a poster, and similarly a short-term boost to the immune system is warranted.

  2. This looks like another of those dubious studies. Why did he use pictures of furniture on the controls, and not pictures of people doing other active things (hitting cricket balls, jumping over hurdles, fornicating, peering into microscopes, etc.)? For all we know — thus far! — just looking at other people, or looking at closeups of other people, or looking at people facing you, stimulates the immune system.

    On next to no evidence, I’m going to blame this second lapse in a month (previous was 22/3) on Discover.

  3. Sarky git 😉 I’m more than happy with the controls. Furniture is an appropriate neutral control – using humans for this purpose would be rubbish. Too many confounds. The point is that the guns act as a second control group. It addresses your issue about looking at other people or at closeups of other people or at people facing you. The fact that images of sneezing elicited a three-fold stronger reaction on top of the gun images suggests something specifically related to disease, rather than generally related to people/portraits/threat.

  4. So, regarding the news story I heard this morning about an increase in measles infections in the US due to people electing not to vaccinate can be countered by showing all unvaccinated children photos of people suffering from very bad cases of measles?

    And regarding Martin’s line — I’m going to print a great big letter A for my daughter’s upcoming exams…can’t hurt, might help. Of course, I won’t make her wear it or anything. Especially not in scarlet.

    Just kidding folks, she IS my daughter! And I love her even though she is a teen!

  5. A study group of only 28 people is NOT enough to draw any kind of conclusion. I’m surprised that Discovery even looked at this. Anyone who has taken statistics knows that to be a decent study group you need at least 100 people to draw an extrapolated conclusion for a larger population.

    This is an interesting theory and I’d like to see more studies done, but this is hardly news worthy.

  6. You’ll note that I called it a small study right from the second paragraph and said that they needed to do a “larger follow-up study using more volunteers” in the penultimate one.

  7. Similar is well known for allergic reactions, sounds or pictures
    related to the allergen can trigger a somewhat weaker allergic

  8. So what are the implications for people with skin diseases, eg excema or psoriasis? If i have a rash on my leg, and looking at the rash triggers my immune system..causing more of a rash…? Ought we to be treating diseases by preventing people looking at them to avoid extra strain on the immune system?
    what are the implications for hospitals? Do they work not by healing people but by giving them sicker people to look at? Or is seeing sick people causing more illness and stress to those in hospital?
    does it make hayfever a social disease? Are people more likely to get it if they know other people who have it?

  9. Interesting idea.

    The experimenters concluded that the difference in response to gun images and to sickness images was due to the appropriateness of the subject matter to the task of the immune system, and not due to a general difference in anxiety levels produced (as measured by a questionnaire).

    However, a couple of other important differences between the stimuli should be noted:
    1. An image of a gun would have been meaningless in our environment of evolutionary adaptedness (EEA), and
    2. For most of us, any potential reaction to seeing sickness in our immediate environment could have been sensitized by occasional exposure during the course of our lives. Much fewer people ever held directly in front of their face.

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