What Causes a Psoriasis Flare
Psoriasis flares are triggered by multiple factors including stress, systemic infections, medications (particularly lithium, antimalarials, beta-blockers, and NSAIDs), mechanical trauma, and abrupt withdrawal of systemic corticosteroids or cyclosporine. 1, 2
Classic Triggering Factors
Infections
- Streptococcal infections, particularly tonsillar Streptococcus pyogenes, strongly induce guttate psoriasis and can exacerbate chronic plaque disease 3
- Skin and gut colonization by Staphylococcus aureus, Malassezia, and Candida albicans have been linked to disease exacerbation 3
- Systemic viral infections, including respiratory tract infections and COVID-19, can trigger flares through direct inflammatory cytokine activation 1, 4
- Erythrodermic psoriasis carries significant risk of staphylococcal septicemia 1
Medications That Precipitate or Worsen Psoriasis
- Lithium, chloroquine, and mepacrine may cause severe, even life-threatening deterioration 1, 2
- Beta-blockers and NSAIDs are common culprits in some patients 1, 2, 3
- Antimalarial agents (hydroxychloroquine, chloroquine) can precipitate flares, though clinical significance remains uncertain 1, 2, 3
- ACE inhibitors, interferon, gemfibrozil, iodine, digoxin, and clonidine have documented associations with exacerbation 2, 3
- Alcohol is both a behavioral trigger and independent risk factor for onset and severity 1
Iatrogenic Triggers
- Abrupt withdrawal or dose reduction of systemic corticosteroids can trigger severe flares, including potentially life-threatening generalized pustular psoriasis or erythrodermic exacerbations 5, 6
- Withdrawal or reduction of cyclosporine in chronic plaque psoriasis patients has caused transformation to erythrodermic or generalized pustular psoriasis 7
- Discontinuation of immunosuppressive treatments during acute infections removes disease control, allowing flare development 4
Environmental and Physical Factors
- Mechanical stress and trauma (Koebner phenomenon) can induce new lesions 8
- Psychological stress is a well-documented trigger 1, 8, 9
- Environmental pollution contributes to disease exacerbation 8
Metabolic and Hormonal Factors
- Hormonal alterations can influence disease activity 8
- Metabolic disturbances associated with obesity and metabolic syndrome may worsen psoriasis 8, 9
Emerging Risk Factors
Biologic Therapy-Related
- Loss of efficacy over time may occur with all TNF-alpha antagonists, resulting in flares after initial control 1
- Paradoxical psoriasis induction with TNF-alpha antagonists can cause pustular psoriasis even in patients without prior psoriasis history 6
COVID-19 Related
- SARS-CoV-2 infection may result in psoriasis flares based on case reports, though clinical significance is not fully understood 1, 4
- The mechanism involves direct inflammatory triggering through overlapping cytokine pathways with psoriatic disease pathophysiology 4
Critical Clinical Pitfall
Before attributing a psoriasis flare to disease progression, ensure it is not due to an undiagnosed concomitant disease affecting immune responses 10. This is particularly important when considering escalation of immunosuppressive therapy, as underlying infections or malignancy may masquerade as treatment failure.
Pathophysiologic Context
The chronic inflammation in psoriasis develops through epidermal infiltration and activation of type 1 and type 17 Th cells, with the IL-23/Th17 immune axis serving as the key driver 9. Environmental triggers activate these pathways, leading to the characteristic erythematous plaques with silvery scale 11, 9. Understanding these mechanisms explains why diverse triggers—from infections to stress to medication withdrawal—can all precipitate flares through convergent inflammatory pathways.