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 itching occurs with trouble breathing, faintness, or swelling of your lips, tongue, mouth, or throat.
These may be signs of a severe allergic reaction.
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 same-day medical advice if:
A rash is rapidly spreading, painful, blistering, or peeling
A rash affects your eyes, mouth, or genitals
You have fever or feel very unwell with the rash
The skin is increasingly painful, hot, swollen, or leaking pus
Itching began after a new medicine and you also have a widespread rash
Your skin or eyes look yellow, especially with dark urine or pale stools
If you are pregnant, contact your maternity team promptly about new widespread itching, especially if it affects your palms or soles, is worse at night, or occurs without a rash.
And for anyone, someone who:
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 itching lasts more than a few weeks, keeps returning, affects most of your body, disrupts sleep, or has no clear cause.
You should also arrange an appointment if self-care is not helping or scratching has damaged your skin.
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 Itchy skin. If you are not sure, err upward — it is always reasonable to be checked.