Pathway

Calm skin barrier

Atopic dermatitis↓

The Barrier That Overreacts

1 blend on this site modulates it.

Also searched as Eczema · Atopic dermatitis.

The skin barrier and the Th2 response feed each other. Blocking the IL-4 receptor interrupts that loop, which is what the approved antibody does.

In depth

Atopic dermatitis — itching, inflamed skin driven by the allergic arm of the immune system.

What drives it

Allergic signaling increases it.

Atopic dermatitis is an IL-4/IL-13 disease, shown interventionally: dupilumab is a monoclonal antibody against the shared alpha subunit of the IL-4 receptor, blocking both IL-4 and IL-13 signaling, FDA-approved for moderate-to-severe atopic dermatitis and sustaining improvement in signs, symptoms and quality of life for up to five years (PMC11954541). Blocking one receptor pair controls the disease. The route is JAK/STAT-mediated repression of barrier genes FLG, LOR, IVL, CLDN1 and AQP3, giving impaired keratinocyte differentiation, tight-junction disruption and increased permeability -- now drawn explicitly as the JAK → Atopic Dermatitis link. filaggrin null mutation is itself associated with barrier dysfunction and raised AD risk independent of cytokine signaling, and IL-17E (IL-25) suppresses filaggrin synthesis in keratinocytes -- so the barrier defect has genetic and non-Th2 contributors this arrow does not carry. Th22 and Th17 responses also contribute to chronic AD lesions, especially in pediatric, intrinsic and Asian patients. PMC11954541

Cytokine signaling increases it.

Verified at source (Pharmacol Res 2025, doi 10.1016/j.phrs.2025.107968 / S0753332225007024): in AD, increased allergen penetration and Th2 cytokine signaling — notably IL-4 and IL-13 — drive jak/stat-mediated repression of skin-barrier genes including filaggrin (flg), loricrin (lor), involucrin (ivl), claudin-1 (CLDN1) and aquaporin-3 (AQP3), producing impaired keratinocyte differentiation, tight-junction disruption and increased skin permeability. This names the route by which the cytokine reaches the tissue, which the direct IL-13 arrow leaves implicit. The finding that matters most here, and it cuts both ways: blocking one axis can convert the disease into the other. Targeting the TNF/IL-17/23 axis in psoriasis, or the IL-4/13 axis in atopic dermatitis, can produce a phenotypic shift toward the opposite disease. In dupilumab-treated AD patients (IL-4/IL-13 blockade), plasma IL-17A and TNF-alpha were significantly elevated versus healthy controls and tslp remained persistently high — consistent with reported psoriasiform eruptions on dupilumab, understood as a shift toward Th1/Th17 dominance once Th2 is suppressed (PMC12968250). Suppressing a dominant pathway can unmask alternative immune axes. Psoriasis and AD also share a final common pathway of barrier-gene repression and barrier fragility despite opposite immune profiles. doi 10.1016/j.phrs.2025.107968 · PMC12968250

Skin reduces it.

The barrier is not downstream - it is half the loop. Defects in skin barrier-related molecules interact with the polarization of T cells, which forms a skin barrier-inflammatory loop with them. This loop contributes to the chronicity of the primary disease OR the transition between psoriasis and AD. IL-4 and IL-13 potently inhibit filaggrin, LORICRIN and INVOLUCRIN by activating STAT6 and STAT3 - the cytokines break the barrier, the broken barrier admits more allergen, more allergen drives more cytokine. doi 10.3389/fimmu.2025.1541776 · PMC11007107

Immune support reduces it.