Your eyes may be the window to your soul, but your skin is the window to your health. When you are healthy and vibrant, you generally have radiant and glowing skin. When you are ill, you may find that you start to have an unhealthy pallor or break out into rashes. This demonstrates the many connections your skin has to other systems in your body, including that between your skin and brain.
The nervous system and the skin develop concurrently in the womb, so it comes as no surprise that the two remain closely connected in life. There is an entire area of dermatology known as psychodermatology that looks at this connection in action. There are generally three categories of this type of patient: those whose skin diseases are precipitated or exacerbated by psychological stress, those who have dermatological symptoms as part of their psychiatric disorder, and those who have a significant psychological impact from their skin disorder that may be more detrimental than their physical symptoms.
The interactions between your skin and brain are not just one way; studies point to a two-way conversation between the two. In fact, many researchers now believe the skin is a neuroendocrine organ in its own right. Let’s dive into the literature to learn a bit more.
The Skin as a Neuroendocrine Organ
The skin continually comes into contact with the environment, more so than the other components of the body. Therefore, it continually has to react to environmental stressors to facilitate systematic homeostasis, and its responses are not always under control of the central nervous system (CNS).
There is a range of hormones, neuropeptides, and neurotransmitters in the skin, including:
- Growth hormone
- Thyroid-stimulating hormone (TSH)
The skin also contains the associated receptors, demonstrating it not only synthesizes but also receives these signals.
The skin is enervated, so it receives these hormones, neurotransmitters, and neuropeptides from the CNS through the cutaneous nerve endings. These nerve fibers are mostly sensory in nature and are part of the autonomic nervous system, generally falling under the sympathetic system. However, these are also produced locally as part of the neuroendocrine system and peripheral HPA axis.
The skin neuroendocrine responses have the capacity to work locally and systemically. The system works in a hierarchical manner similar to the brain axes in the body, and it may be left over from evolution, since many simple organisms have similar neuroendocrine systems in the skin to react to stressors.
Thus, the brain and skin speak to one another, leading to the formation of a brain-skin axis. The skin also can work autonomously to react as needed to environmental stressors it comes in contact with, especially as it also has an immune system and a stress response connected to the HPA axis.
HPA Axis and the Skin
The skin contains a peripheral HPA axis that mirrors the main HPA axis, including corticotropin-releasing hormone (CRH), POMC-derived peptides, glucocorticoids, and receptors for these signals. The keratinocytes in the skin can release stress hormones, such as cortisol, CRH, and ACTH, as well as neurotransmitters and neurotrophins. Skin cells also have receptors for these molecules. This helps the skin to sense and react to the environment, including temperature, injuries, pH, and humidity.
In the skin, CRH acts as a proinflammatory cytokine to create increased permeability and inflammation, most likely due to mast cell activation. It also stimulates the release of IL-6 and mast cells and influences proliferation, differentiation, and apoptosis of skin cells. CRH can also be anti-inflammatory through modulating angiogenesis, cytokine production, and vascular permeability. The activation of stress response through releasing cortisol or corticosterone leads to a reduced function of the skin barrier, reducing its efficiency as a protector and antimicrobial agent. The breakdown of steroidogenic potential can also lead to skin disorders.
Neurotransmitters in Action on the Skin
In addition to having its own HPA axis, the skin also contains its own nervous system that releases neurotransmitters locally, and the skin cells respond to neurotransmitters and hormones released by the CNS. The neurotransmitters play different roles in the skin:
- Acetylcholine—Regulation of keratinocyte homeostasis
- Dopamine—potentially immunomodulatory
- Endocannabinoids—Anti-inflammatory, anti-tumorigenic, helps with chronic pain, reduces itching, modulates the release of other hormones and neurotransmitters to help regulate both skin and systematic homeostasis
- Histamine—modulates the function of keratinocytes, melanocytes, and immune cells in the skin; affects intracellular signaling cascades, melanogenesis, and cell proliferation; modulates Th2 immune responses and the expression of antimicrobial peptides
- Melatonin—Regulation of hair growth cycle, skin physiology, skin pathology, and cutaneous pigmentation; protective role as an antioxidant
- Serotonin—Vasoactive, immunomodulatory effects, stimulates proliferation, transforms light energy into biological reactions
This is a short list of the key activities of the nervous system in the skin. As you can see, maintaining a healthy neuroendocrine system in your skin can help to maintain the overall health of your largest organ.
Keeping Your Skin’s Neuroendocrine System Healthy
As interesting as it is that your skin has its own brain, how does this translate into practical action? For one, it demonstrates the importance of your skin health on your overall homeostasis, as well as the potential negative impact of excessive stress on your skin.
So, what can you do to help? Start by consuming a healthy, plant-based, colorful diet that provides the essential nutrients and phytochemicals to maintain your overall health and wellbeing. Key nutrients for your skin and nervous system include:
- Essential fatty acids (especially omega-3)
- Support for glutathione
- Vitamin A
- Vitamin C
- Vitamin D
- Vitamin E
Additionally, avoid food that might irritate your skin, impact your HPA axis, induce brain fog or other cognitive symptoms, or which you may otherwise negatively react to. Exercise and adequate hydration may also help support your healthy skin and nervous system, which likewise will support the neuroendocrine system of your skin. Also, it is key to have a healthy gut. As I discussed in another blog, there is an important connection between the gut and skin as well: the brain-gut-skin axis.
Once you have the foundation of your core health, take some time to review your stress levels, especially in relation to your skin health. Stress has been shown to be associated with several skin disorders, including psoriasis, rosacea, lichen planus, alopecia areata, pruritus, and atopic dermatitis. Stress also can delay the healing of skin, including barrier recovery. If there is any psychological aspect of your skin disorder, whether a cause or effect, work on it, ideally with a dermatologist and/or psychologist familiar with psychodermatology. Handling any psychological stress or psychiatric disorders has been shown to improve skin problems.
- Ayurvedic medicine
- Cognitive-behavioral therapy
- Homeopathic medicine
- Mindfulness meditation
- Stress reduction
- Traditional Chinese medicine
Before you implement anything, discuss this with your doctor or another healthcare practitioner to discover the best course of action for your unique needs.