Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services or go to an emergency department now if you develop a painful or rapidly spreading rash with blisters, peeling skin, fever, or sores in the mouth or eyes.
Emergency assessment is also needed for:
Trouble breathing, swallowing, or staying awake
Severe eye pain, light sensitivity, or sudden vision changes
Signs of dehydration, such as very little urine or marked dizziness
Widespread skin tenderness or detachment
Rapid swelling of the face, tongue, or throat
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
This is especially urgent after starting a medicine.
After discharge, seek prompt medical advice for increasing wound redness, pus, returning fever, worsening pain, reduced urine, or new eye symptoms.
These may indicate infection or another complication.
3
Does any of this apply?
Book an appointment
Routine follow-up is appropriate for ongoing dryness, skin colour changes, nail problems, mild scar discomfort, or emotional concerns that are not rapidly worsening.
Keep planned appointments with dermatology, eye care, and other specialists.
The article also says
Do not drive yourself if you are very unwell.
Take all medicine containers or an up-to-date medicine list if it is safe to do so.
Every sign above is quoted from the sofidex article on Stevens johnson syndrome. If you are not sure, err upward — it is always reasonable to be checked.