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https://www.goodreads.com/notes/48664152-the-remarkable-life-of-the-skin/114528832-mark-gerstein?ref=abp

1 The Swiss Army Organ
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About half of people with severe eczema have a mutation in the filaggrin gene, and while it’s not the only reason for this complex disease–the outside environment and internal immune system are other causes–we now know that barrier dysfunction is a prime factor. 4 Towards the Light
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Importantly, in the same way that crowded commutes bring together a diverse population, the sunlight that hits your nose is made up of different photons, each with differing characteristics determined by its wavelength. The human eye can detect the wavelengths of visible light, enabling you to see the slight sunburn on the tip of your nose. The particles of sunlight that actually bring about the burn, however, are invisible, high-energy, ultraviolet (UV) rays. The majority of UV light that reaches the Earth’s surface is made up of UVA particles. These penetrate beyond the outer layer of our skin and cause damage to the deeper dermis. Over time this weakens the skin’s supporting layer of collagen and elastin, causing wrinkles, leathery skin and pigmented spots in a process known as photoageing.
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Current research suggests that although many people who are severely sunburned as children never develop skin cancer, one blistering sunburn in childhood increases the risk of melanoma later on in life by 50 per cent. 3 Another study suggests that white women (the study did not look at men) who get five or more severe sunburns in their teens have double the risk of developing melanoma. 4
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After Catriona had left, the oncologist turned to me. ‘As humans we’re notoriously bad at assessing risk, particularly when it comes to our future health,’ he observed. ‘But when it comes to someone under your care … I think that a bad sunburn on an infant is nothing short of child abuse.’
6 The First Sense
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Interestingly, the brain’s map of the sensory skin seems jumbled up, and the amount of brain used is not related to the surface area of the body the skin covers. For example, the skin on the fingertip of our forefinger, with its considerable density of sensory receptors, requires the attention of a proportionally much larger area of our brain’s ‘skin map’ than, say, the skin on our back. To represent this, Penfield created a model of a human where the appendages of the body were either shrunk or enlarged to represent the amount of space they occupy in the brain. The result was the sensory homunculus–a gangly, off-balance, ‘grotesque creature’ (as Penfield described it) with enlarged body parts where there is a high density of mechanoreceptors (hands, feet and lips), in contrast to those where there are far fewer (such as the torso and arms), which are spindly and diminutive. The brain’s map of the body ever since has been called the sensory homunculus.
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Recent research also suggests that the pleasant activation of this emotional touch-system positively modulates our own sense of body ownership. 14 This has been shown using the ‘rubber hand’ illusion. (If you happen to be in possession of a lifelike plastic limb, this also makes for an impressive party trick.) Subjects put their right hand on a table in front of them and keep their left hand hidden from view behind a screen, with a rubber hand on the table in its place. Their hidden left hand and the rubber hand in place of their left are then stroked at the same time. When subjects are stroked with the speed and lightness of emotional touch, they are more likely to perceive the rubber arm as their own. 15
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Our inability to self-tickle demonstrates that our brain can exert a subconscious force on our physical feelings that we cannot control. It might be logical, then, to think that our sensory skin is subservient to our brain; that our body is incidental to the power of our mind. To show that this isn’t the case, try some of these easy illusions. First, place your left hand in a bowl of icy water and your right in hot (but not scalding) water. After a full two minutes, take them both out and dip them into a third bowl, of tepid, room-temperature water. For a moment our perception of reality is disturbed–one hand thinks that the third bowl of water is cold, the other hot–and it’s unsettling. In a similar way, if you simultaneously rub one hand along a piece of smooth plastic and the other across rough carpet and then place both hands on a wall, one hand tells you that the wall is rough, the other that it is smooth. Even though both hands are sensing the same temperature or feeling the same surface, each hand gives the brain a different answer. This shows that the brain gives in to what each hand is telling it. The brain adapts to serve the needs of the skin.