In one of his articles, Professor Laurent Misery, head of the Neurobiology Laboratory at the University of Western Brittany in France, described the connection very precisely: “The skin and the central nervous system are embryological siblings that remain nostalgic for one another. The skin is not simply a collection of different layers and cells that provide covering and protection; it is part of the nervous and immune systems and responds very actively to constantly changing environmental stimuli.” In other words, the skin can be viewed as an external extension of the nervous system.
As a complex neuro-immune-endocrine structure, the skin is permeated by a vast number of different receptors. Its sensory apparatus includes free nerve endings that are sensitive to pain, mechanical pressure and irritation. Each receptor is specialised for a particular tactile sensation, but several receptors are activated at the same time to perceive sensations such as touch.
In addition, many receptors can perceive related sensations as well: the same receptor may respond to friction and, for example, pressure or temperature. This allows the body to react to external stimuli more quickly and effectively.
How Does the Connection Between the Skin and Brain Appear in Practice?
The simplest example is to remember how prolonged stress and increased nervous tension can be accompanied by eczema or dermatitis, or how the skin of the face may look after a lack of sleep, which is also a form of stress for the body.
During stress, skin cells and nerve endings, including C-fibres, release a special class of molecules called neurotransmitters, which transmit nerve impulses towards the brain. Many of these signalling substances are neuropeptides:
- substance P,
- MSH (melanocyte-stimulating hormone),
- calcitonin gene-related peptide,
- endorphins.
These substances are detected by sensory neurons and can activate the sympathetic nervous system, which is part of the wider nervous system. When signalling molecules reach certain levels, the nervous system can trigger the release of pro-inflammatory neuropeptides into the surrounding tissue, initiating neurogenic inflammation. Cells of the immune system become actively involved, blood vessels dilate, swelling and itching may occur, and the skin can become red — symptoms familiar to many people with reactive or sensitive skin.
