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 if a rash comes with:
Trouble breathing, wheezing, faintness, or tightness in the throat
Rapid swelling of the lips, tongue, face, or throat
Severe weakness, confusion, or difficulty waking
These may be signs of a serious allergic reaction or another emergency.
And for anyone, someone who:
has lips or skin that look pale, blue, grey or blotchy
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 you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek urgent medical care the same day if the rash:
Is painful, rapidly spreading, blistering, or causing skin to peel
Comes with fever and you feel very unwell
Affects the eyes, mouth, or genitals
Looks like purple or dark spots that do not fade when pressed
Appears after starting a medicine and is widespread or worsening
Has increasing warmth, swelling, pain, pus, or red streaks
Occurs in a newborn or in someone with a weakened immune system
And for anyone, someone who:
has a fever with a stiff neck, a rash that does not fade under pressure, or severe headache
has a wound that is hot, spreading red, or leaking pus
3
Does any of this apply?
Book an appointment
Book a routine appointment if the rash lasts more than a few weeks, keeps returning, spreads gradually, disturbs sleep, or does not improve with basic care.
You should also arrange an assessment if you are unsure what triggered it or it may be linked to work, medicines, or a long-term skin condition.
And for anyone, someone who:
has noticed a lump, a mole that has changed, or unexplained weight loss
Every sign above is quoted from the sofidex article on Skin rash. If you are not sure, err upward — it is always reasonable to be checked.