Autumn rain: being damp is inferred rather than truly felt. Photo: Getty
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On our nerves: what makes us itch or feel wet?

Michael Brooks’s science column. 

We’re all going to feel some unwanted damp on the skin over the next few weeks – welcome to autumn. But for those who feel wet due to a medical condition rather than the weather, researchers at Loughborough University have made what might just prove to be a welcome breakthrough.

It starts with a seemingly innocuous question: what makes wet stuff feel wet? By the end of this exploration, we will have encountered Joni Mitchell, patients with multiple sclerosis (MS) and a host of people suffering in ways that evoke Dante’s Inferno.

To some animal species, wetness is so critical to survival that evolution has equipped them to determine their state of external hydration: insects have humidity sensors. Human beings, however, don’t have wetness sensors on their skin, so understanding how we differentiate the sense of wetness from other sensations is a puzzle.

We have found clues in some of the tricks one can play on our species. The Loughborough researchers have shown that if you reduce the skin’s temperature using a dry cooling method, people feel as though their skin is wet. If you put something wet in contact with the skin, but at a temperature warmer than it, people don’t perceive it as wet.

So, clearly, we don’t feel wetness, we infer it. Our skin has an array of sensors for temperature and pressure, and it is a combination of these senses which tells us that something we are touching is wet. To find out what that combination might be, the Loughborough team experimented on 13 students, blocking and releasing their nerve sensitivities.

It turns out that crucial to wetness perception are nerves known as A-nerve fibres. Block the blood supply to these – using something like a blood-pressure cuff – and you become far worse at sensing wetness. Unsurprisingly, it is easier to sense cold wetness than warm wetness. The interplay of these different sensitivities enabled the researchers to create a model for the brain’s interpretation of wetness; in essence, it applies a weighting to each set of inputs in order to come to a probability-based conclusion on the body’s state.

This is more than an academic discovery because skin sensitivity is a serious medical issue. People suffering with MS frequently report an unpleasant feeling of cold wetness on their skin. It is a couple of short steps from feeling cold wetness to pain. One side effect of diabetes, for instance, can be dysaesthesia, when diabetics experience a burning or stabbing sensation on their skin, or feel the slightest touch from clothing or bedlinen as excruciating pain. In other cases, some diabetics can’t feel heat or touch sensitively enough to avoid injuring themselves.

It’s not just about the side effects of recognised diseases, though. There are various medical conditions associated with nerves sending pain signals in response to (apparently) nothing. Sufferers of central pain syndrome can report sensations such as being torn apart with hot knives, or being burned alive. No wonder it gets referred to as a Dante-type condition. Another oddity is Morgellons Disease. Joni Mitchell is perhaps the best-known sufferer of this unstoppable itching, which feels as if something is crawling under the skin. The medical orthodoxy is that the condition is indicative of a psychiatric disorder. However, if we knew more precisely what our skin’s nerve endings transmit to the brain, we might be able to help sufferers, delusional or not. 

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 08 October 2014 issue of the New Statesman, Grayson Perry guest edit

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Beesic Instinct: Labour wants to protect the bees from Brexit

Leaving the EU could weaken protections, which is a shame because politicans have a lot to learn from hive behaviour

No more bumbling around from Labour: the Party is now firmly pro-Bee. Their new manifesto says they would ban the controversial pesticides, known as neonicotinoids or “neonics”, from the UK:

The pledge is not just great news for bees, whose nervous systems are attacked by the chemicals, but for admirers of bees' elegant political decision making too. In fact, if our politics was more bee-like perhaps it would bug us less.

Bees, it turns out, are skilled in the political arts. When honey bees have to move to a new hive they send “scouts" to check out the options - a cosy crevice in your shed perhaps. The scouts then relay their findings to their comrades with a “waggle dance” up the honeycomb walls. Their sequence of steps indicates a site’s location, and if their opinion of your shed is not so hot, they’ll only bother to repeat their dance a couple of times. If they love it, they can dance a few hundred.

The longer a bee dances, the larger her audience grows. Her fellow scout bees can then follow the directions and visit the venue themselves. On their return, they perform their opinion for others. Eventually a hive should end up with a critical mass of the creatures all dancing for the same place. At that point, the entire hive takes flight to its new, democratically elected, home. Talk about waxing lyrical. 

Now just think about what such a system could do for British politics? Leaving aside the joyful prospect of our Right-Honourables jigging their way through parliament, would bees be vague about what kind of EU relationship they were choosing? No way. Would they have been swayed by dodgy facts? Nope. 

But, wait, what’s that I hear you say? – it’s not real democracy if only the scout bees get a vote! Fair point. But in that respect, neither is our own: just take 16 year-olds or foreign nationals. 

Plus the sad truth is that leaving the EU is putting the UK's capacity for strong, scientific decision making in doubt - not least over which pesticides are safe to use.

At present, The European Food Saftey Authority evaluates the safety of the substances proposed in new “plant protection products” and shares the results among the member states. In 2013, its findings led the European Commission to restrict the use of three key neonictides which the EFSA warned posed a “high acute risk” to honey bee health. This science has recently been reviewed by the EFSA and may see the restrictions extended to a complete ban

In the event of Brexit, the UK will have to decide on whether or not to maintain, extend or reduce EU rulings on pesticides. Labour's call for prohbiition is in line with calls from seventeen of the UK’s leading environment and conservation groups (the Green Party already pledged to ban neonoictinoids in their 2015 campaign). But while the Conservative government says it will take a "risk based" approach to the matter, it is under pressure from pesticide and farming groups to relax present regulation. In 2013 it also voted against the EU’s partial ban.

The even wider question, however, is how Britain will conduct scientific reviews and licensing in future. Dave Timms, senior policy campaigner for Friends of the Earth, is concerned about what our future relationship to the EFSA's review process will be: "You've got so many chemicals coming up for review all the time that member states take it in turn to be rapporteurs - and that process of sharing the science, sharing the effort, could be lost if we leave."

Even Defra has highlighted the problem of repatriating such decisions to the UK: "some areas (such as chemicals or ozone-depleting substances) might present more challenges than others because they are currently delivered by EU agencies, systems or resources,” it said in evidence presented for a recent government report.

The need for decisions based on shared and transparent scientific evidence has thus arguably never been greater. Otherwise we risk a situation in which, as Dr Elli Leadbeater of Royal Holloway told the NS, “evolution seems to have found a better solution than we have.”

India Bourke is an environment writer and editorial assistant at the New Statesman.

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