Unflame
Psoriasis

Psoriasis: why plaques come back where they do

Psoriasis runs on the IL-23/Th17 immune axis and has a memory. These explainers cover what cleared skin is still holding, why injury can seed a plaque weeks later, and what the gut-skin story does and does not show.

Explainers

Pattern stories about psoriasis

Psoriasis

Why psoriasis comes back in the same spot

Cleared psoriasis plaques leave an invisible footprint of resident immune cells and altered genes.

Read the explainer Eczema · Psoriasis

The gut-skin axis is real. 'Your skin disease starts in your gut' is not what it shows.

Gut microbes, the intestinal barrier and circulating immune signals do communicate with the skin.

Read the explainer Psoriasis

Why a scratch can turn into a psoriasis plaque, and why most scratches don't

Skin injury can trigger a new psoriasis plaque at the exact site 1 to 3 weeks later.

Read the explainer Tracking

What a symptom log can tell you, and what it cannot

Memory inflates past symptoms, exposures happen together, and flares change your sleep and stress rather than the reverse.

Read the explainer

What the evidence supports, in one place

  • Cleared plaques are not biologically cleared. Resolved skin keeps resident memory T cells (5 to 16 times more than healthy skin), altered fibroblasts and a molecular scar of 200+ genes. In the only body-mapping study, about 60% of returning plaque area fell inside old borders; the "90%" figure traces to unpublished data.
  • Stopping treatment is the most predictable relapse trigger in trial data, with a median of about 15 weeks to loss of control after biologic withdrawal in one study. Any change belongs in a conversation with your dermatologist.
  • Injury localises plaques (the Koebner phenomenon) one to three weeks later, but most injuries do not: in the largest controlled test, 72.5% of people developed no plaque from ten needle pricks.
  • Gut-skin: psoriasis microbiome studies contradict each other, one specific probiotic mixture showed an adjunct effect while a six-month single-strain trial showed none, and faecal transplant did worse than sham in psoriatic arthritis.

Red flags that need a clinician

Widespread sterile pustules or redness over most of the body, especially with fever or feeling unwell, is an emergency. Guidelines also recommend annual screening for psoriatic arthritis and cardiovascular risk checks for severe disease.

Every figure above is sourced and discussed in the linked explainers. This page summarises; it does not add claims.

Written by Laxmanna · Research-led health writer. Every explainer on Unflame starts from a structured evidence dossier: primary studies retrieved, claims tabulated, contradictions logged, and wording checked against what the sources can support. How the dossiers are built.