When you think of your immune system, you may imagine an army of cells deep in your bloodstream working to eradicate any viruses or bacteria you may encounter.
You probably don’t imagine similar cells marching up and down your arm, but you could.
That’s because the skin is a complex organ that not only provides a strong external barrier against environmental assaults, but also hosts of variety of cells that help mount immune system responses against a variety of attackers.
Yes, your skin is part of your immune system, and if it’s not as healthy as it should be, it’s not only your appearance that suffers—you may also lose some protection against infection and disease.
The Skin Contains Important Immune Cells
The human body is blessed with a network of cells, tissues, and organs that work together to protect it. This network is called the immune system, and it’s responsible for keeping us healthy.
When foreign substances like viruses or bacteria (called antigens) invade the body, the immune system detects them and sends cells off to dispatch them as quickly as possible. White blood cells called lymphocytes produce antibodies, which are specialized proteins that lock onto the bad guys and mark them for destruction. If all goes well, the enemy is soon defeated and the system relaxes until the next invader emergency.
While much of this goes on inside the bloodstream, immune action takes place on and within the skin, too. Key immune cells in the epidermis—the outer layer of skin—include:
- Epidermal dendritic cells (Langerhans cells): These cells help mount defensive weapons against skin infections.
- Keratinocytes: These are skin cells that help form a barrier against parasites, fungi, viruses, and bacteria.
In the deeper layers of the skin—the dermis—we find more immune cells, including:
- Dermal dendritic cells: These are similar to the dendritic cells above, with the only difference being they reside more deeply in the skin.
- Lymphocytes: These are white blood cells that function as one of the skin and body’s main types of immune cells. There are several different types that work together to eradicate threats, including B cells and T cells.
- Mast cells: These are immune cells that release histamine and other substances during inflammatory and allergic reactions. These reactions help destroy pathogens.
These cells move in and out of the skin, lymph nodes, and bloodstream, keeping everything safe and protected.
The Skin Also Has Beneficial Bacteria
There is also a community of beneficial bacteria on the skin—much like that which exists in the gut—called the microbiome. This community helps fortify the barrier that keeps skin healthy, and also helps keep the immune system up to speed as to what it should attack and what it should leave alone.
If this system is disturbed, such as through excessive sterilization or the overuse of antibacterial soaps, it can upset the immune system and increase risk of skin infections and out-of-balance immune reactions, such as sensitivity and allergic reactions.
Interestingly, recent studies have also discovered that the health of the microbiome in the gut can play a major role in immunity, such that it affects the skin, too. In a 2017 study, for example, researchers found that differences in microbiome between different individuals could be associated with the development of psoriasis.
How the Immune System Affects the Skin
When the immune system is working well, the skin is strong and protective. It keeps you safe from infections and diseases—including skin cancer—and it isn’t overly sensitive or reactive.
When the immune system is not working as it should, however, things can go wrong. Below are a few of the most common problems:
- Psoriasis: As noted above, psoriasis is a known immune system problem. For reasons currently unknown to scientists, the immune system stimulates the overproduction of certain cells that cause red and flaky patches of skin.
- Allergic contact dermatitis: The immune system sees what is usually recognized as a normal or harmless compound as a threat, and mounts a defense against it, causing systems like inflammation, swelling, and redness.
- Eczema: Recent research has discovered that eczema may be the result of an overactive immune system. Immune proteins in the skin mistakenly target the body’s own tissues, causing those itchy, scaly lesions. A 2015 study, for example, found that a treatment aimed at calming this reaction helped reduce symptoms of eczema.
- Infections: Skin infections may be the result of a weakened skin barrier or lackluster immune system unable to eradicate the cause of the infection.
- Allergic reactions: Inflammation, hives, and rashes that develop in response to an allergic trigger are the result of an immune system that is attacking a substance that may not be harmful. Sometimes, the immune cells will start to see fragrances or other chemicals as invaders, whereas before they were allowed to exist peacefully.
- Itching: If your skin is itching and you can’t find any clear cause, this could also be caused by a malfunctioning immune system. One study showed that an imbalanced immune system could be at the root of this issue.
These are only a few of the conditions that may be related to the skin’s immune system—we are learning about more all the time. Meanwhile, what can you do to keep your skin immune system working optimally?
How to Help Keep the Skin’s Immune System Working Optimally
Sometimes, the immune system reacts abnormally because of genetics or something else that we don’t really have control over. There are some things we can do, though, to help support this army in the skin:
- Avoid antibacterial soaps. Stick with warm water and regular soap and cleansers.
- Eat a healthy diet and make sure you’re getting enough probiotic foods like yogurt, kefir, sauerkraut, miso, tempeh, and other fermented foods.
- Regularly participate in stress-relieving activities like meditation, tai chi, yoga, walking, and journaling.
- Get out and start a garden—interaction with dirt has been shown to help support the immune system, particularly in young children.
- Make sure you’re getting enough vitamin D, either from sun exposure or from supplements.
- Use safe products with real ingredients that work naturally with the skin—avoid chemicals that irritate and damage skin.
Did you know that the skin was part of your immune system?
Hamilton, J. D., Suárez-Fariñas, M., Dhingra, N., Cardinale, I., Li, X., Kostic, A., … Guttman-Yassky, E. (2014). Dupilumab improves the molecular signature in skin of patients with moderate-to-severe atopic dermatitis. Journal of Allergy and Clinical Immunology, 134(6), 1293-1300. doi:10.1016/j.jaci.2014.10.013
Washington University. (2017, November 6). Itching for no reason? Immune system may be at fault | The Source | Washington University in St. Louis. Retrieved from https://source.wustl.edu/2016/05/itching-no-reason-immune-system-may-fault/
Yan, D., Issa, N., Afifi, L., Jeon, C., Chang, H., & Liao, W. (2017). The Role of the Skin and Gut Microbiome in Psoriatic Disease. Current Dermatology Reports, 6(2), 94-103. doi:10.1007/s13671-017-0178-5