SOURCED · CITED · NEVER MEDICAL ADVICE
Home  /  Glossary  /  Cytokine storm
GLOSSARY · INFLAMMATION

Cytokine storm

A self-amplifying, dysregulated release of inflammatory signaling proteins that overwhelms normal regulation and damages tissue. Implicated in severe COVID-19 pneumonia and a recognized clinical syndrome long before COVID-19.

Edited by M. Callahan · Last reviewed 2026-05-10

How researchers study it

"Cytokine storm" entered the medical literature in the 1990s describing graft-versus-host disease, and has since been applied to sepsis, hemophagocytic lymphohistiocytosis, CAR-T cell therapy reactions, and severe viral pneumonias. A widely cited 2020 NEJM review by Fajgenbaum and June lays out a unifying framework — elevated circulating cytokines, immune cell hyperactivation, and systemic inflammation that drives organ dysfunction (Fajgenbaum & June, NEJM, 2020).

In severe COVID-19, researchers consistently measure elevated interleukin-6 (IL-6), interleukin-1 beta, tumor necrosis factor (TNF), and C-reactive protein in plasma from critically ill patients (Huang et al., Lancet, 2020, PubMed 32125452). The pattern partially overlaps with sepsis but has some COVID-specific features, and the field has debated whether the term "cytokine storm" is fully accurate or whether COVID-19 hyperinflammation should be classified separately.

Therapeutically, drugs targeting cytokine signaling have been tested in severe COVID-19. Tocilizumab and sarilumab (IL-6 receptor antagonists) and baricitinib (JAK inhibitor) showed mortality benefit in hospitalized patients on supplemental oxygen in large randomized trials such as RECOVERY and REMAP-CAP — establishing that dampening specific cytokine pathways can improve outcomes in selected patients.

Common misconceptions

"All severe COVID-19 is a cytokine storm."Hyperinflammation contributes to severe disease in many patients, but the magnitude and pattern vary, and not all critically ill COVID patients meet the same cytokine criteria.
"Cytokines are the enemy."Cytokines are essential signaling molecules. The problem is dysregulation — too much of certain signals at the wrong time — not the molecules themselves.
"You can detect a cytokine storm at home."It is diagnosed in hospital with laboratory measurements (IL-6, ferritin, CRP, D-dimer) and clinical context. Home symptoms are not diagnostic.
WHAT THIS DOES NOT MEAN This entry describes a clinical inflammation syndrome studied in hospitalized patients. It is not a claim that any supplement, food, or wellness protocol prevents or treats a cytokine storm. Severe inflammation requires emergency medical care.
RELATED TERMS

Continue across the glossary

RELATED READING

From the journal

SOURCES
  1. Fajgenbaum DC, June CH. "Cytokine Storm." New England Journal of Medicine, 2020. nejm.org
  2. Huang C et al. "Clinical features of patients infected with 2019 novel coronavirus in Wuhan." Lancet, 2020. PubMed: 32125452
  3. RECOVERY Trial. recoverytrial.net
Informational only · Not medical advice This entry describes a clinical syndrome studied in hospital settings. It does not diagnose, treat, or prevent disease. Severe symptoms need medical attention — call a clinician or emergency services.