DRESS Syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms)

DRESS syndrome — Drug Reaction with Eosinophilia and Systemic Symptoms — is a rare, severe, life-threatening drug hypersensitivity reaction that sets itself apart from other drug reactions by its delayed onset, widespread organ involvement, and a characteristic interplay with human herpesvirus reactivation. Also called Drug-induced Hypersensitivity Syndrome (DiHS), DRESS carries a mortality rate of 10–20%, most commonly from acute liver failure. Unlike Stevens-Johnson Syndrome, DRESS does not cause epidermal necrosis or skin detachment; instead, the damage is systemic — liver, kidneys, lungs, heart — driven by drug-specific T-cell activation amplified by reactivating viruses including HHV-6, EBV, and CMV. Understanding the delayed 2-to-8-week onset is critical: patients frequently fail to connect a drug started six weeks ago with the illness now in front of them.

  1. What Is DRESS? Distinguishing It from Other Drug Reactions
  2. Causative Drugs and High-Risk Medications
  3. Pathophysiology: T-Cell Activation and Herpesvirus Reactivation
  4. Clinical Features: Rash, Facial Edema, Fever, and Visceral Involvement
  5. Diagnosis: RegiSCAR Criteria and Laboratory Workup
  6. Organ Involvement: Liver, Kidney, Lung, and Heart
  7. Treatment: Drug Withdrawal, Corticosteroids, and Prolonged Tapering
  8. Cross-Reactivity, Drug Avoidance, and Long-Term Follow-Up
  9. Key Research Papers
  10. Connections
  11. Featured Videos

What Is DRESS? Distinguishing It from Other Drug Reactions

DRESS is a distinct clinical syndrome within the spectrum of severe cutaneous adverse reactions (SCARs). The four main SCARs — DRESS, Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and Acute Generalized Exanthematous Pustulosis (AGEP) — differ in mechanism, causative drugs, timeline, and the type of tissue damage they cause. Recognizing the differences is a matter of clinical urgency because the management diverges sharply.

The key distinguishing features of DRESS are:

Estimated incidence is 1 in 1,000 to 1 in 10,000 drug exposures for high-risk drugs. Mortality is 10–20% overall but approaches 40% when fulminant hepatic failure develops.

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Causative Drugs and High-Risk Medications

Not all drugs cause DRESS equally. A relatively defined list of medications carries substantially elevated risk. Exposure to any of these drugs in a patient presenting with fever, rash, facial edema, lymphadenopathy, and eosinophilia should immediately direct attention to the possibility of DRESS:

Aromatic Anticonvulsants — Anticonvulsant Hypersensitivity Syndrome

Carbamazepine, phenytoin, lamotrigine, and phenobarbital are the most historically recognized DRESS-causative drugs. DRESS from these agents was previously called "anticonvulsant hypersensitivity syndrome" before the unified DRESS terminology was established. A critical clinical fact: aromatic anticonvulsants cross-react with each other in DRESS. A patient who develops DRESS on carbamazepine has approximately 40–80% cross-reactivity with phenytoin and phenobarbital. Lamotrigine cross-reacts less predictably but the risk remains. After DRESS from any aromatic anticonvulsant, all drugs in that class must be avoided, and a neurologist must select a structurally unrelated antiepileptic.

Allopurinol

Allopurinol — used for gout and hyperuricemia — is one of the most common causes of DRESS worldwide, particularly in Asia. The HLA-B*58:01 allele confers a dramatically increased risk of allopurinol-associated DRESS and Stevens-Johnson Syndrome in Han Chinese, Thai, Korean, and Vietnamese populations. The FDA and multiple Asian national guidelines now recommend HLA-B*58:01 screening before initiating allopurinol in patients of Asian descent. The alternative, febuxostat, does not appear to share this HLA-associated risk.

Sulfonamides and Dapsone

Trimethoprim-sulfamethoxazole (TMP-SMX) is a leading sulfonamide cause of DRESS, particularly in HIV-positive patients who have historically required high-dose TMP-SMX for Pneumocystis pneumonia prophylaxis. Dapsone — used for leprosy, dermatitis herpetiformis, and malaria prophylaxis — causes a well-described DRESS-like reaction called "dapsone syndrome" with hepatitis and methemoglobinemia as additional features.

Abacavir

The antiretroviral abacavir causes a systemic hypersensitivity reaction — clinically overlapping with DRESS — in patients carrying HLA-B*57:01. Abacavir hypersensitivity was historically fatal in some rechallenge cases. Prospective HLA-B*57:01 screening before prescribing abacavir has essentially eliminated abacavir hypersensitivity in screened populations and is now mandated internationally. This represents one of the earliest and most successful examples of pharmacogenomic screening preventing a severe drug reaction.

Vancomycin

Vancomycin-induced DRESS is increasingly recognized, particularly in patients receiving prolonged IV courses. It can co-occur with vancomycin-induced linear IgA bullous dermatosis, complicating the clinical picture. Teicoplanin is a safer alternative glycopeptide in patients with vancomycin DRESS.

Minocycline

The tetracycline-class antibiotic minocycline — widely used for acne — causes a well-described DRESS syndrome with particular prominence of autoimmune features: positive ANA, lupus-like serology, and hepatitis. Young women with prolonged minocycline use for acne are the typical affected population.

Checkpoint Inhibitors

Immune checkpoint inhibitors (PD-1 inhibitors: pembrolizumab, nivolumab; CTLA-4 inhibitors: ipilimumab) cause immune-related adverse events (irAEs) that can closely mimic DRESS, with eosinophilia, rash, hepatitis, and pneumonitis. Distinguishing true DRESS from checkpoint inhibitor irAEs is important because treatment differs (steroids are cornerstone in both, but drug rechallenge decisions differ fundamentally).

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Pathophysiology: T-Cell Activation and Herpesvirus Reactivation

The pathophysiology of DRESS is more complex than a simple drug allergy. Three interacting mechanisms appear to work in concert:

Drug-Specific T-Cell Activation

The initiating event is activation of drug-specific cytotoxic CD8+ T cells and helper CD4+ T cells. The drug or its reactive metabolite is presented to T cells in association with HLA molecules — either through direct binding to HLA (pharmacological interaction / p-i concept) or through covalent haptenation of self-proteins. T-cell clonal expansion takes 2–8 weeks, explaining the delayed onset. These activated T cells then infiltrate target organs — liver, kidney, lung, skin — and drive tissue damage through perforin/granzyme-mediated cytotoxicity and cytokine release (TNF-α, IFN-γ, IL-5, IL-13).

Eosinophil Recruitment

IL-5 produced by activated T helper cells drives the characteristic eosinophilia. Eosinophils infiltrate tissues and release toxic granule proteins (major basic protein, eosinophil cationic protein) that directly damage hepatocytes, renal tubular cells, and myocardium. The degree of eosinophilia correlates imperfectly with organ damage severity — some patients with severe hepatitis have only mild eosinophilia, and vice versa.

Herpesvirus Reactivation — The Distinguishing Feature

During the course of DRESS, latent herpesviruses — primarily HHV-6 (human herpesvirus 6, which infects nearly 100% of humans by age 2 and persists latently in mononuclear cells) but also EBV, CMV, and HHV-7 — reactivate sequentially. HHV-6 reactivation typically occurs 2–4 weeks after DRESS onset. The reactivating virus provides additional antigenic stimulation, recruits more immune effectors, and may directly infect organ-specific cells (hepatocytes, cardiac myocytes). This herpesvirus-drug immune interaction creates a feed-forward cycle that explains why DRESS continues to worsen — and can relapse — long after the causative drug is stopped. The sequential pattern of viral reactivation (HHV-6 first, then EBV or CMV) has been documented in Japanese series and has diagnostic and therapeutic implications: serial HHV-6 PCR titers track DRESS activity and may inform treatment decisions regarding antiviral therapy.

The HLA associations observed in DRESS (HLA-B*58:01 in allopurinol DRESS; HLA-A*31:01 in carbamazepine DRESS in Europeans; HLA-B*57:01 in abacavir hypersensitivity) reflect the specific HLA-drug-peptide binding that enables T-cell activation, explaining why DRESS is not a universal response to these drugs but is highly predictable in genetically susceptible individuals.

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Clinical Features: Rash, Facial Edema, Fever, and Visceral Involvement

DRESS typically unfolds over days to weeks after a latency period of 2–8 weeks from the start of the causative drug. The clinical presentation integrates cutaneous, systemic, and laboratory findings:

Fever

High fever — 38.5 to 40°C — is typically the first sign and often precedes the rash by several days. The fever is sustained and does not resolve without drug withdrawal and treatment. In the context of a new drug started weeks prior, unexplained high fever should prompt consideration of DRESS.

Skin Eruption

The rash begins as a morbilliform (maculopapular) eruption on the face and upper trunk, spreading centrifugally to involve more than 50% of body surface area. The eruption is confluent, erythematous, and may become edematous. Importantly, the skin does not blister or peel in sheets — this absence of epidermal detachment distinguishes DRESS from SJS/TEN. Some patients develop follicular accentuation, purpuric components, or vesicles, but Nikolsky sign is negative. Exfoliative dermatitis (generalized skin scaling) may develop in severe or prolonged cases.

Facial Edema

Periorbital and facial puffiness — often described as a "puffy face" or "swollen face" appearance — is a characteristic and clinically distinctive feature of DRESS that is rarely emphasized in textbooks but is highly recognizable to experienced clinicians. The edema is non-pitting and involves the periorbital region, cheeks, and lips. Patients look systemically ill and puffy, quite different from the usual morbilliform drug rash in an otherwise well-appearing patient.

Lymphadenopathy

Generalized lymphadenopathy — enlarged, tender lymph nodes in cervical, axillary, and inguinal chains — is present in the majority of DRESS cases. Lymph node biopsy, if performed, shows reactive hyperplasia with immunoblasts and eosinophils; biopsy is rarely needed for diagnosis but may be obtained to exclude lymphoma.

Mucosal Involvement

Unlike SJS/TEN where extensive mucosal erosions are a hallmark, mucosal involvement in DRESS is mild when present: mild oral erosions, cheilitis, or pharyngeal erythema. Extensive mucosal blistering should prompt reconsideration of SJS/TEN rather than DRESS.

The Relapsing-Remitting Course

A clinically puzzling and dangerous feature of DRESS is its tendency to worsen or relapse after drug withdrawal, sometimes for weeks to months. Liver enzymes that were improving may spike again. New organ involvement (renal, pulmonary) can emerge after the initial cutaneous eruption resolves. This relapsing course is attributed to ongoing herpesvirus-driven immune activation that persists after the triggering drug is gone.

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Diagnosis: RegiSCAR Criteria and Laboratory Workup

No single diagnostic test confirms DRESS. Diagnosis is clinical and requires integration of history, physical examination, and laboratory findings. The RegiSCAR scoring system provides a validated framework:

RegiSCAR Criteria for Probable or Definite DRESS

All of the following must be present: hospitalization + suspected drug reaction + acute skin rash. Plus at least three of the following five criteria:

  1. Fever above 38.5°C
  2. Enlarged lymph nodes in at least two sites
  3. Involvement of at least one internal organ (liver, kidney, lung, heart)
  4. Blood count abnormalities: eosinophilia (above 1,500/µL or above 10%), atypical lymphocytes, lymphopenia or lymphocytosis
  5. Skin rash extending beyond 50% body surface area, or characterized by at least two of: facial edema, purpura, exfoliation, or skin biopsy showing features compatible with DRESS

A score of 4 = "probable DRESS"; 5 or 6 = "definite DRESS."

Laboratory Workup

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Organ Involvement: Liver, Kidney, Lung, and Heart

Visceral involvement in DRESS is what kills. Identifying which organs are affected guides severity assessment and treatment intensity:

Hepatitis (Most Common — Present in 50–80%)

Hepatic involvement ranges from asymptomatic transaminase elevation to fulminant hepatic failure. Transaminases (AST, ALT) commonly reach 5–20 times the upper limit of normal; values above 20-fold elevation signal severe hepatitis. Cholestatic patterns (alkaline phosphatase, bilirubin elevation) occur less commonly. Drug-induced autoimmune hepatitis — a prolonged autoimmune hepatitis persisting after DRESS resolution — can follow DRESS, particularly in HHV-6-associated cases, requiring months of immunosuppressive treatment after the acute episode. Liver failure is the principal cause of DRESS-related death; patients with progressive hyperbilirubinemia and coagulopathy (INR elevation) require urgent hepatology consultation and ICU-level monitoring.

Nephritis

Interstitial nephritis (tubulointerstitial nephritis with eosinophilic infiltrate on biopsy) occurs in 10–30% of DRESS cases. Rising creatinine and proteinuria are the early signals. Urinalysis may show eosinophiluria, though this finding has low sensitivity. Most cases of DRESS nephritis respond to corticosteroids; a minority develop chronic kidney disease requiring prolonged immunosuppression or, rarely, dialysis.

Pneumonitis

Pulmonary DRESS manifests as interstitial pneumonitis with bilateral ground-glass infiltrates on CT, hypoxemia, and dry cough. Eosinophilic pneumonia pattern may be seen on bronchoalveolar lavage. Severe cases require supplemental oxygen; mechanical ventilation is rarely necessary. Pulmonary involvement is more common with minocycline DRESS and dapsone DRESS than with anticonvulsant-associated cases.

Myocarditis and Pericarditis

Cardiac DRESS is the rarest but most acutely lethal organ involvement. Eosinophilic myocarditis can cause rapid-onset heart failure, arrhythmia, or cardiogenic shock. Troponin elevation in the context of DRESS should prompt urgent echocardiography and cardiology consultation. HHV-6 myocarditis may co-occur with drug-induced eosinophilic myocarditis, compounding the injury. Endomyocardial biopsy showing eosinophilic infiltrate confirms the diagnosis but is rarely performed acutely given procedural risk. High-dose corticosteroids are the treatment; IVIG and plasmapheresis have been used in refractory cases.

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Treatment: Drug Withdrawal, Corticosteroids, and Prolonged Tapering

Management of DRESS requires prompt recognition, immediate drug withdrawal, organ-targeted supportive care, and immunosuppression. The severity of organ involvement determines treatment intensity:

Step 1 — Immediate Drug Withdrawal

The causative drug must be stopped immediately. This is the single most important intervention. Early drug withdrawal — within 48 hours of recognizing DRESS — is associated with shorter disease course and lower organ injury severity. However, because DRESS continues its course after drug withdrawal (driven by viral reactivation), stopping the drug alone is rarely sufficient treatment for moderate-to-severe cases.

Step 2 — Identify and Stop All Non-Essential Drugs

Many DRESS patients are on polypharmacy. Any drug started within the past 8 weeks that is not immediately life-sustaining should be considered a suspect and stopped or substituted. In ambiguous cases with multiple candidate drugs, all should be stopped if clinically feasible.

Step 3 — Systemic Corticosteroids

Systemic corticosteroids are the mainstay of DRESS treatment. Prednisone 0.5–2 mg/kg/day (or equivalent IV methylprednisolone in severe or hospitalized cases) reduces organ inflammation, suppresses eosinophilia, and attenuates the T-cell-driven tissue damage. Most patients show significant clinical improvement — fever breaks, rash fades, transaminases fall — within 1–2 weeks of starting corticosteroids.

A critical caution: corticosteroids may increase the risk of herpesvirus reactivation or replication. Some experts delay steroids until HHV-6 serology and PCR results are available; others start steroids empirically in severe cases while awaiting viral testing. There is no consensus on this question. The balance of evidence favors early corticosteroids in organ-threatening DRESS despite the theoretical viral risk.

Step 4 — Prolonged Taper (8 to 12 Weeks Minimum)

This is where DRESS management most often goes wrong. Rapid steroid tapering — finishing a 2-week prednisone course as one might for poison ivy or a morbilliform rash — reliably triggers DRESS relapse. The relapse manifests as re-elevation of liver enzymes, return of fever and rash, or new organ involvement. The taper must be slow — typically 2–3 months — with the dose held or reversed at the first sign of relapse. Patients and outpatient physicians must be explicitly warned that DRESS is not a short-course disease.

Antiviral Therapy for HHV-6

When HHV-6 PCR titers are high and organ damage is progressive despite corticosteroids, some experts add antiviral therapy targeting HHV-6. Ganciclovir (IV) or valganciclovir (oral) are active against HHV-6, though clinical trial evidence is limited to case series and retrospective analyses from Japan. The decision to add antivirals is made case-by-case in severe DRESS with documented high HHV-6 replication.

Supportive Care

Hospitalization is required for moderate-to-severe DRESS. IV fluid resuscitation for dehydration from fever and poor oral intake; standard wound care for the skin eruption (moisturizers, non-irritating topical agents; no corticosteroid creams needed as systemic steroids address the skin); close monitoring of renal function, liver enzymes, and complete blood count during treatment; ophthalmology consultation if eye involvement (usually mild in DRESS); nutrition support if oral intake is compromised.

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Cross-Reactivity, Drug Avoidance, and Long-Term Follow-Up

Surviving DRESS carries lasting implications that require careful long-term management:

Drug Avoidance for Life

The causative drug must be permanently avoided. Rechallenge with the inciting drug is absolutely contraindicated and can cause a rapid, severe, and fatal recurrence. Patients must receive written documentation of the reaction and the specific drug to avoid.

Cross-Reactivity Within Drug Classes

Cross-reactivity between structurally related drugs is clinically important. Aromatic anticonvulsants (carbamazepine, phenytoin, phenobarbital) cross-react at rates of 40–80%; all should be avoided after DRESS from any one of them. Lamotrigine cross-reactivity is less certain but real. Non-aromatic anticonvulsants (valproate, levetiracetam, gabapentin, pregabalin, topiramate) are structurally distinct and do not cross-react — they are the alternatives after anticonvulsant-associated DRESS. Sulfonamide cross-reactivity exists between sulfonamide antibiotics but generally not between sulfonamide antibiotics and sulfonamide non-antibiotics (furosemide, thiazides).

Medical Alert Identification

Patients with DRESS should wear a medical alert bracelet or carry an allergy card listing the causative drug and drug class to avoid. Emergency physicians must know about the reaction before prescribing anticonvulsants for new-onset seizures or antibiotics for acute infections.

Autoimmune Sequelae

DRESS survivors have an elevated risk of developing de novo autoimmune diseases — autoimmune thyroiditis, autoimmune hepatitis, type 1 diabetes, lupus-like syndromes — months to years after the acute DRESS episode. This autoimmune diathesis is thought to reflect bystander immune activation during the herpesvirus reactivation phase that breaks self-tolerance. Long-term follow-up with thyroid function tests, autoimmune screening, and liver function monitoring is recommended in all DRESS survivors, particularly those with documented HHV-6 reactivation.

Pharmacogenomic Testing for Future Drug Prescriptions

After DRESS, pharmacogenomic testing (HLA typing) should be offered to the patient and first-degree relatives who may need the same drug class. HLA-B*58:01 carriers who have never received allopurinol should be prescribed febuxostat as an alternative. HLA-A*31:01 carriers of European descent requiring anticonvulsants should receive non-aromatic alternatives. This proactive testing prevents DRESS in the next generation of the family.

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Key Research Papers

  1. Bocquet H, Bagot M, Roujeau JC. Drug-induced pseudolymphoma and drug hypersensitivity syndrome (Drug Rash with Eosinophilia and Systemic Symptoms: DRESS). Semin Cutan Med Surg. 1996;15(4):250–257. PMID: 9069593
  2. Cacoub P, Musette P, Descamps V, et al. The DRESS syndrome: a literature review. Am J Med. 2011;124(7):588–597. PMID: 21592453
  3. Kardaun SH, Sekula P, Valeyrie-Allanore L, et al. Drug reaction with eosinophilia and systemic symptoms (DRESS): an original multisystem adverse drug reaction. Results from the prospective RegiSCAR study. Br J Dermatol. 2013;169(5):1071–1080. PMID: 23855313
  4. Shiohara T, Inaoka M, Nagata Y. Drug-induced hypersensitivity syndrome (DIHS): a reaction induced by a complex interplay among herpesviruses and antiviral and antidrug immune responses. Allergol Int. 2006;55(1):1–8. PMID: 17075281
  5. Descamps V, Valance A, Edlinger C, et al. Association of human herpesvirus 6 infection with drug reaction with eosinophilia and systemic symptoms. Arch Dermatol. 2001;137(3):301–304. PMID: 11255327
  6. Tassaneeyakul W, Jantararoungtong T, Chen P, et al. Strong association between HLA-B*5801 and allopurinol-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in a Thai population. Pharmacogenet Genomics. 2009;19(9):704–709. PMID: 19696706
  7. Mallal S, Phillips E, Carosi G, et al. HLA-B*5701 screening for hypersensitivity to abacavir. N Engl J Med. 2008;358(6):568–579. PMID: 18256392
  8. Blumenthal KG, Youngster I, Rabideau DJ, et al. Peripheral blood eosinophilia and hypersensitivity reactions among patients receiving outpatient parenteral antibiotics. J Allergy Clin Immunol. 2015;136(5):1288–1294. PMID: 26033891
  9. Walsh SA, Creamer D. Drug reaction with eosinophilia and systemic symptoms (DRESS): a clinical update and review of current thinking. Clin Exp Dermatol. 2011;36(1):6–11. PMID: 21143513
  10. Chen YC, Chiu HC, Chu CY. Drug reaction with eosinophilia and systemic symptoms: a retrospective study of 60 cases. Arch Dermatol. 2010;146(12):1373–1379. PMID: 21173313
  11. Fiszenson-Albala F, Auzerie V, Mahe E, et al. A 6-month prospective survey of cutaneous drug reactions in a hospital setting. Br J Dermatol. 2003;149(5):1018–1022. PMID: 14632809
  12. Husain Z, Reddy BY, Schwartz RA. DRESS syndrome: Part I. Clinical perspectives. J Am Acad Dermatol. 2013;68(5):693.e1–14. PMID: 23602182

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Connections

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