DRESS - drug reaction with eosinophilia and systemic symptoms

DRESS · DIHS · drug-induced hypersensitivity syndrome · drug hypersensitivity syndrome

A late, multi-organ drug reaction - the rash is the least dangerous part; the liver, kidney and heart are what kill.

ADMITBand A

Red flags

Any widespread drug rash with fever - check FBC, liver and renal function before discharge
Eosinophilia or transaminitis in a patient with a new rash
A rash appearing weeks rather than days after a drug is started - the median latency in RegiSCAR was 22 days (IQR 17-31), so a drug history covering only the last few days will miss the culprit
Chest pain, dyspnoea or hypotension - myocarditis is a recognised and lethal complication

Recognise

On light skin

Widespread red morbilliform or urticarial-looking eruption becoming confluent, infiltrated and oedematous, with a swollen face and later desquamation.

On brown and black skin

Confluent erythema may be hard to appreciate and the eruption can read as generalised darkening or a violaceous, ashen change instead of redness. Facial oedema, skin infiltration that makes the surface feel thickened, and the tone-independent systemic features are the reliable signs. Post-inflammatory hyperpigmentation during resolution is more pronounced and more persistent, and should not be mistaken for ongoing active disease.

In any skin tone

Facial oedema - a hallmark, and unusual in a simple drug rash
High fever and lymphadenopathy
Eosinophilia, atypical lymphocytes, or deranged liver function on routine bloods
A long latency: median 22 days after starting the drug in the prospective RegiSCAR series, far longer than most drug rashes
Mild mucosal involvement may occur but severe erosions point to epidermal necrolysis instead

Distribution

Widespread morbilliform eruption, often becoming confluent and oedematous, classically with marked facial swelling. Frequently involves over half the body surface (a conventional description - no proportion in the references cited here supports a specific threshold).

Photographs

DRESS: a dense maculopapular eruption on the back of the hand, in the case reported it began peripherally and spread centrally. On its own t — DRESS: a dense maculopapular eruption on the back of the hand, in the case reported it began peripherally and spread centrally. **On its own this looks like an ordinary drug rash, and that is the trap** - what makes it DRESS is not the appearance of the skin but what is happening elsewhere: fever, facial swelling, lymphadenopathy, eosinophilia and deranged liver function, beginning two to six weeks after the drug rather than within days.
Fitzpatrick I-III (Fitzpatrick type estimated from the photograph, not stated by the source) · Ilahi HB, Baloch MB, Kasfiki E · Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS) Due to Trimethoprim: A Case Report. Cureus 2025;17 · CC BY 4.0

The same eruption spreading onto the trunk and becoming confluent. Extensive involvement, and skin that is swollen and infiltrated rather th — The same eruption spreading onto the trunk and becoming confluent. **Extensive involvement, and skin that is swollen and infiltrated rather than flat, are what separate this from a simple exanthem.** Examine the face for oedema and feel for nodes; the diagnosis is made by the systemic findings and the bloods, not by the rash.
Fitzpatrick I-III (Fitzpatrick type estimated from the photograph, not stated by the source) · Ilahi HB, Baloch MB, Kasfiki E · Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS) Due to Trimethoprim: A Case Report. Cureus 2025;17 · CC BY 4.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Stevens-Johnson syndrome / toxic epidermal necrolysis — Both severe drug reactions; epidermal necrolysis blisters and erodes mucosa, DRESS swells and involves organs
Toxic shock syndrome — Both give fever and a widespread eruption; TSS is shocked and rapid, DRESS has a latency of weeks and eosinophilia
Erythroderma — DRESS is a cause of erythroderma rather than a separate thing when it becomes confluent

What to do in the ED

Stop the suspected drug immediately - and search back weeks, not days, because the latency is long
Take FBC with differential, liver function, renal function, CRP and a urine dip: the diagnosis is made on bloods, not on the rash
ECG and troponin if there is any cardiorespiratory symptom, because myocarditis can present late and is a leading cause of death
Assess against the RegiSCAR criteria rather than diagnosing on impression
Refer to dermatology and admit - this is not a rash to review in clinic
Do not restart the culprit or a cross-reacting drug; document the reaction prominently in the allergy record
Warn about the relapsing course: this reaction can flare weeks after the drug is stopped

Score

RegiSCAR DRESS criteria — the calculator is in the interactive tool.

Disposition

ADMIT

Admit under medicine with dermatology input. Organ involvement dictates the level of care.

Sources

Open this entry in the interactive tool