Written by Aisha Saleem, Pharmacist & Health Writer at PharmaHealths.com
Last Updated: July 2026
One of the most common questions I get after explaining a psoriasis or eczema diagnosis to a patient is some version of: “But why is my immune system attacking my own skin?” It’s a fair question, and the honest answer is that the immune system isn’t quite doing that in the way most people imagine. What’s actually happening is more nuanced and, once you understand it, the logic behind modern biologic treatments becomes much clearer. The immune system drives chronic skin inflammation not through a single malfunction but through a cascade of signaling events involving specific cells, cytokines, and pathways that become stuck in a cycle of overactivation. Understanding how that cycle works is the foundation for understanding why treatments like Dupixent, Cosentyx, and JAK inhibitors are designed the way they are.
What Is Chronic Inflammation and How Is It Different from Acute Inflammation?
Chronic inflammation is a sustained, often dysregulated immune response that persists beyond the point where it serves a useful protective function. Acute inflammation is the normal, short lived immune response to injury or infection, producing redness, swelling, heat, and pain as the immune system sends cells and mediators to clear pathogens and initiate healing. Chronic inflammation occurs when that response fails to resolve, either because the trigger persists, the immune system is dysregulated, or the inflammatory cycle becomes self-sustaining even without the original trigger.
According to the National Institute of Allergy and Infectious Diseases, chronic inflammation is a core feature of conditions including psoriasis, atopic dermatitis, rheumatoid arthritis, and inflammatory bowel disease, all of which share the common thread of immune pathways that have become chronically overactive rather than self-limiting.
How Does the Immune System Normally Protect the Skin?
The skin is the body’s largest immune organ, housing a highly specialized network of immune cells that serve as the first line of defense against pathogens, allergens, and environmental damage. The skin immune system has two arms:
• The innate immune system, which provides rapid, non-specific responses.
• The adaptive immune system, which mounts slower but highly targeted responses involving T cells and antibodies.
In healthy skin, innate immune cells including mast cells, dendritic cells, macrophages, and natural killer cells detect potential threats and trigger downstream immune signaling when needed. T lymphocytes, the central players in the adaptive response, are then activated and differentiate into distinct subsets depending on the signals they receive, each driving a different type of immune response. Research published in Nature Reviews Immunology has established that the balance between these T cell subsets, particularly Th1, Th2, and Th17 cells, is a key determinant of whether the skin remains healthy or develops chronic inflammatory disease.
What Are Cytokines and Why Do They Matter in Skin Disease?
Cytokines are signaling proteins produced by immune cells that act like communication signals between cells, coordinating the immune response. In skin disease, cytokines are the molecular messengers that tell skin cells to proliferate faster, tell immune cells to migrate to the skin, and amplify or resolve inflammation. Understanding which cytokines drive which conditions is the entire basis of modern biologic therapy, since each biologic drug works by blocking one or more of these specific signals.
The American Academy of Dermatology recognizes that cytokine imbalances are central to nearly all chronic inflammatory skin diseases. In psoriasis, the key cytokines are IL-17, IL-23, and TNF-alpha, which drive rapid skin cell proliferation and sustain the inflammatory plaque cycle. In atopic dermatitis, IL-4 and IL-13 are the dominant cytokines, driving the allergic-type Th2 immune response that disrupts the skin barrier and fuels the itch-scratch cycle. These differences in cytokine profiles explain why a drug that works brilliantly for psoriasis may have little to no effect on eczema, and vice versa.
How Does the Immune System Drive Psoriasis Specifically?
In psoriasis, chronic inflammation begins when innate immune cells, particularly dendritic cells, are activated by triggers including infections, skin injury, or stress, and release IL-23. According to research published in the Journal of Investigative Dermatology, IL-23 is the key upstream cytokine that activates and sustains Th17 cells, a subset of T lymphocytes that produce large amounts of IL-17A. IL-17A then acts on keratinocytes, the predominant cells of the skin’s outer layer, driving rapid proliferation and further cytokine release.
This self-amplifying inflammatory loop, where IL-23 drives IL-17 production, which drives keratinocyte proliferation, which triggers more cytokine release, is what maintains psoriasis as a chronic condition rather than a self-resolving one. It also explains why biologic drugs targeting IL-17 or IL-23 are so effective: blocking either signal interrupts the cycle at a critical control point. Research published in the New England Journal of Medicine consistently shows that interrupting this pathway allows the inflammatory cascade to gradually wind down and the skin to clear.
How Does the Immune System Drive Eczema Differently?
In atopic dermatitis, the immune pathway follows a different pattern. The starting point is a combination of genetic skin barrier dysfunction, particularly involving the filaggrin protein that maintains barrier integrity, and an overactive Th2 immune response driven by IL-4 and IL-13 signaling. According to the National Eczema Association, when the skin barrier is compromised, allergens and irritants penetrate more easily, triggering Th2 cells to release IL-4 and IL-13, which further weaken the barrier and amplify inflammation.
The itch scratch cycle in eczema is itself an immune driven process. Scratching causes further skin damage, allowing more allergen penetration and triggering more immune activation, creating a reinforcing loop. IL-31, another cytokine produced by Th2 cells, is directly responsible for the intense itch sensation, which is why treatments targeting the Th2 pathway reduce both inflammation and itch severity.
Why Does Chronic Skin Inflammation Cause Problems Beyond the Skin?
Chronic immune activation in skin diseases like psoriasis does not stay confined to the skin. The cytokines produced in psoriatic plaques, particularly IL-17, IL-23, and TNF-alpha, enter systemic circulation and contribute to inflammation in blood vessels and joints. Research published in Frontiers in Immunology has established that this systemic inflammatory burden explains the increased cardiovascular risk, metabolic syndrome, and psoriatic arthritis risk seen in patients, a phenomenon often referred to as the psoriatic march.
In eczema, the systemic dimension is less pronounced but still present. Severe atopic dermatitis is associated with increased rates of asthma, allergic rhinitis, and food allergies, all driven by the same underlying Th2 immune dysregulation.
Why Do Biologics Work Better Than Steroids for Immune Driven Skin Disease?
Biologics work better than steroids for moderate to severe immune driven skin disease because they target specific cytokine pathways rather than broadly suppressing the immune system. Corticosteroids suppress inflammation across multiple pathways, which is effective for short term control but associated with well documented long term side effects.
Biologics like dupilumab, secukinumab, and risankizumab interrupt one or two specific cytokine signals that are central to the disease mechanism, leaving the rest of the immune system largely functional. This targeted approach is why biologics consistently outperform older systemic treatments in terms of both efficacy and long-term tolerability.
The Bottom Line
Chronic skin inflammation in conditions like psoriasis and eczema is not a simple malfunction. It’s a precise network of immune signals, cytokines, and cell interactions that has become locked in a self-sustaining cycle. Understanding which cytokines drive which condition is not just academic, it’s the reason modern treatment can now target disease mechanisms with a level of precision that was not possible with older therapies. If you’re living with a chronic inflammatory skin condition, understanding the immune biology behind your diagnosis is one of the most empowering steps you can take before your next dermatologist visit.
FAQs
Q1: How does the immune system cause chronic skin inflammation?
The immune system causes chronic skin inflammation through the overproduction of cytokines, signaling proteins including IL-17, IL-23, IL-4, and IL-13, that activate immune cells and skin cells in a self-sustaining inflammatory cycle. In psoriasis, this involves Th17 cells and IL-17 driving rapid skin cell proliferation. In eczema, Th2 cells and IL-4 and IL-13 drive barrier breakdown and the itch scratch cycle.
Q2: What are cytokines and why do they matter in skin disease?
Cytokines are signaling proteins produced by immune cells that coordinate the immune response. In chronic skin diseases, specific cytokines including IL-17, IL-23, IL-4, and IL-13 become chronically overproduced, sustaining inflammation that the body cannot resolve on its own. Modern biologic drugs work by blocking these specific cytokine signals, which is why they are more effective than broadly immunosuppressive treatments.
Q3: What is the difference between Th1, Th2, and Th17 immune responses in skin disease?
Th1 cells drive inflammatory responses associated with autoimmune diseases. Th2 cells drive allergic-type responses and are dominant in atopic dermatitis, producing IL-4 and IL-13. Th17 cells are dominant in psoriasis, producing IL-17A that drives rapid skin cell turnover and plaque formation. The balance between these T cell subsets determines which type of skin disease develops and which treatment pathway is appropriate.
Q4: Is eczema an autoimmune disease or an allergic condition?
Eczema sits at the intersection of both. Atopic dermatitis involves a genetic skin barrier defect combined with an overactive Th2 immune response, which has both allergic and immune-dysregulation components. It is not a classic autoimmune disease where the immune system attacks its own tissues, but it does involve immune pathway dysregulation that modern targeted treatments, including dupilumab, address directly.
Q5: Why does psoriasis increase the risk of heart disease?
Psoriasis increases cardiovascular risk because the cytokines produced in psoriatic skin, particularly IL-17, IL-23, and TNF-alpha, enter systemic circulation and contribute to endothelial dysfunction and atherosclerosis. Research published in Frontiers in Immunology has characterized this as the psoriatic march, where chronic systemic inflammation from active skin disease drives cardiovascular and metabolic comorbidities over time.
Q6: Why do biologics work better than steroids for psoriasis and eczema?
Biologics target one or two specific cytokine signals central to the disease mechanism, leaving the rest of the immune system largely intact. Steroids suppress inflammation broadly across multiple pathways, which limits their long-term use due to side effects. According to the Journal of the American Academy of Dermatology, this targeted precision is why biologics consistently outperform systemic steroids for moderate to severe psoriasis and atopic dermatitis.
Q7: What is the innate immune system’s role in skin disease?
The innate immune system is the first responder in the skin, with dendritic cells, mast cells, and macrophages detecting threats and releasing initial cytokine signals. In psoriasis, innate immune activation by dendritic cells releasing IL-23 is the trigger that sets off the Th17 adaptive immune response and the inflammatory cascade. The innate immune system initiates the cycle that the adaptive immune response then sustains.
Q8: Can chronically skin inflammation cause problems beyond the skin?
Yes. In moderate to severe psoriasis, chronic systemic cytokine elevation is associated with significantly increased risks of cardiovascular disease, psoriatic arthritis, metabolic syndrome, and type 2 diabetes. In eczema, the Th2 immune dysregulation driving skin inflammation is linked to asthma, allergic rhinitis, and food allergies as part of the broader atopic march.
Call to Action
If this article helped you understand the immune biology behind your skin condition, I have covered how these specific pathways are targeted by individual biologic drugs, including Dupixent, Cosentyx, Skyrizi, and Rinvoq, in dedicated guides across PharmaHealths.com. Head over to PharmaHealths.com to explore the full immune and skin health series, where each article is designed to give you the evidence-based information you need to have a more informed conversation with your dermatologist.
Disclaimer
This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your doctor, dermatologist, or pharmacist before starting, stopping, or changing any treatment.
References
• National Institute of Allergy and Infectious Diseases
• Nature Reviews Immunology
• American Academy of Dermatology
• Journal of Investigative Dermatology
• New England Journal of Medicine
• National Eczema Association
• British Journal of Dermatology
• Frontiers in Immunology
• Journal of the American Academy of Dermatology
