Health condition
DRESS syndrome
DRESS (drug reaction with eosinophilia and systemic symptoms) is a severe delayed drug reaction: two to eight weeks after starting the culprit medicine, a widespread rash arrives with fever, facial swelling, enlarged lymph nodes and inflamed internal organs.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
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Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
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Typical onset 2-8 weeks after starting the drug - far later than most people expect a drug reaction
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Features: extensive rash, facial oedema, fever, lymphadenopathy, high eosinophils and deranged liver (or kidney, lung, heart) function
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Leading culprits: carbamazepine, lamotrigine, phenytoin, allopurinol, sulfasalazine, vancomycin and dapsone
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Treatment: stop the drug, supportive care and corticosteroids tapered slowly over weeks to months to prevent relapse; herpesvirus (HHV-6) reactivation can complicate the course
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
DRESS is easy to miss precisely because of its delay: by the time the rash and fever appear, the new anticonvulsant or allopurinol has become part of the background. The syndrome smoulders - eosinophils flood the blood, the liver is the organ most often hit, and reactivation of dormant herpesviruses can drive waves of relapse even after the drug is stopped.
Diagnosis and treatment routes
Diagnosis uses the RegiSCAR criteria (rash extent, fever, lymphadenopathy, eosinophilia, organ involvement) with bloods repeated over days, and the culprit drug must never be re-challenged - first-degree relatives are also counselled about related drugs when anticonvulsants are involved. Systemic corticosteroids with a deliberately slow taper are standard for organ involvement, with ciclosporin or other agents in steroid-refractory cases, and long-term follow-up watches for autoimmune thyroid disease and diabetes that can emerge months later. In much of the UK, a routine NHS referral to the relevant specialist clinic can take several months, whereas an initial appointment with a private consultant is typically available within around two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a dermatologist and acute medical team. Your GP can refer you on the NHS, or you can arrange a private consultation directly.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about DRESS syndrome.
Quick, plain-English answers to what people ask us most.
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What is DRESS syndrome?
DRESS syndrome (drug reaction with eosinophilia and systemic symptoms) is a severe, delayed allergic drug reaction typically occurring two to eight weeks after starting a causative medication, involving skin rash, organ involvement, and characteristic blood changes.
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What causes DRESS syndrome?
It's caused by a delayed hypersensitivity reaction to certain medications, with anticonvulsants, allopurinol, and certain antibiotics among the most commonly implicated drugs, though the exact reason some people develop this severe reaction isn't fully understood.
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What are the symptoms of DRESS syndrome?
Symptoms include an extensive skin rash, fever, swollen lymph nodes, and, importantly, involvement of internal organs (commonly the liver), alongside characteristic blood test changes including elevated eosinophils (a type of white blood cell).
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Is DRESS syndrome dangerous?
Yes, it's a serious, potentially life-threatening reaction due to the risk of significant organ damage, particularly to the liver, which is why prompt recognition and treatment are essential once suspected.
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How is DRESS syndrome treated?
Treatment involves immediately stopping the causative medication, alongside supportive care and, for significant cases, corticosteroid treatment to reduce the inflammatory reaction and protect affected organs.
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Why does DRESS syndrome develop weeks after starting a drug?
Unlike immediate allergic reactions, DRESS involves a delayed immune response that takes time to develop, typically two to eight weeks after starting the causative medication, which can make it harder to immediately connect the reaction to a specific drug.
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How long does recovery from DRESS syndrome take?
Recovery can take weeks to months, and importantly, symptoms can sometimes flare or relapse even after the causative drug is stopped, requiring extended monitoring and, sometimes, prolonged steroid treatment.
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Can DRESS syndrome happen again with the same or similar drugs?
Yes, once a specific drug is identified as the cause, that medication (and sometimes related drugs) should be permanently avoided, and this should be clearly documented in your medical records and communicated to future prescribers.
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DRESS syndrome vs a typical drug rash - what's the difference?
A typical mild drug rash usually doesn't involve organ dysfunction or the characteristic blood changes seen in DRESS syndrome, which is a much more severe, systemic reaction requiring hospital-based assessment and treatment rather than simple reassurance.
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When should I seek help for suspected DRESS syndrome?
Seek urgent medical attention for a widespread rash with fever, particularly if it develops weeks after starting a new medication - this needs prompt hospital assessment given the risk of serious organ involvement.