Severe drug reaction: anaphylaxis vs SJS/TEN case

Two very different emergencies

Severe drug reactions come in different shapes, and telling them apart helps you act. Anaphylaxis is fast: within minutes to an hour of a trigger, the whole body reacts, with breathing and blood pressure most at risk. SJS and TEN are slower and rarer: over days after starting a medicine, the skin and the moist linings of the mouth, eyes and other areas become severely damaged and start to blister and peel. One threatens the airway and circulation almost at once; the other is like a severe burn from the inside, damaging large areas of skin. Both are medical emergencies needing 999 and hospital care, but knowing the pattern — sudden and breathless, versus spreading blistering rash with mouth and eye soreness — helps you recognise trouble early.

Anaphylaxis: the sudden reaction

Anaphylaxis usually starts within minutes of a trigger such as a medicine, food or insect sting. Warning signs include swelling of the lips, tongue or throat, a hoarse voice or difficulty swallowing, noisy or difficult breathing, wheeze, a widespread itchy rash or hives, feeling faint or collapsing, and sometimes tummy pain or being sick. The most dangerous features are trouble breathing and a drop in blood pressure. If someone has these signs, call 999 immediately and say anaphylaxis. If an adrenaline auto-injector is available and the person is prescribed one, it should be used straight away as directed, and a second dose may be needed if there is no improvement after five minutes. Lay the person flat with legs raised (or sit them up if breathing is hard) and stay with them until help arrives.

SJS and TEN: the delayed skin reaction

Stevens-Johnson syndrome and toxic epidermal necrolysis usually begin days to a few weeks after starting a new medicine. They often start with flu-like feelings — fever, sore throat, tiredness and stinging eyes — before a painful red or purplish rash appears and spreads. Blisters form, and the skin begins to peel away, sometimes in large sheets, leaving raw areas like a burn. Crucially, the moist linings are affected too: painful sores in the mouth, sore red eyes, and soreness of other areas are common and important clues. TEN is the most severe form, affecting the largest area of skin. This is a rare but life-threatening emergency. Any spreading blistering rash with mouth or eye involvement soon after a new medicine needs urgent hospital assessment — call 999 or go to A&E.

What happens in hospital

For anaphylaxis, the team give adrenaline and support breathing and blood pressure, watch closely for several hours in case symptoms return, and arrange follow-up to identify the trigger and, where needed, provide auto-injectors and an allergy plan. For SJS or TEN, the suspected medicine is stopped at once, and care is like that for a severe burn: people are often looked after in a specialist burns or intensive care unit, with careful fluid replacement, wound care, pain relief, eye care and prevention of infection. Doctors take a detailed medicine history to find the culprit drug. Both conditions are recorded clearly in the person's records as an allergy or serious reaction so the drug is never given again, and the person is told which medicine to avoid for life.

Staying safe and preventing future harm

The safe pathway is the same for both: treat them as emergencies. Call 999 for sudden breathing difficulty, throat or tongue swelling, faintness or collapse after a medicine — this may be anaphylaxis — and use a prescribed adrenaline auto-injector without delay. Seek emergency care for a spreading, blistering or peeling rash with sore mouth, eyes or fever after starting a medicine, which may be SJS or TEN. Afterwards, make sure the responsible medicine is clearly recorded as an allergy, tell every healthcare professional and pharmacist about it, and consider medical-alert jewellery. Never take a medicine you have reacted badly to before. Recognising these reactions early, acting fast and recording the cause are what prevent the most serious harm.