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
Seek urgent or emergency assessment if fever occurs with rapidly spreading redness, severe swelling, widespread blistering or peeling, difficulty waking, breathing difficulty, or a child who appears seriously unwell.
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 prompt medical care for:
Blisters, pus, open sores, significant bleeding, or honey-coloured crusts
Increasing pain, swelling, warmth, or redness
A rash spreading beyond the diaper area
A bright red rash involving skin folds with separate surrounding spots
Painful redness around the anus
Poor feeding, unusual sleepiness, dehydration, or repeated vomiting
Any fever in a baby younger than 3 months
And for anyone, someone who:
has a fever with a stiff neck, a rash that does not fade under pressure, or severe headache
3
Does any of this apply?
Book an appointment
Arrange routine medical advice if the rash is not beginning to improve after a few days of careful home treatment.
Assessment is also appropriate if the cause is unclear, the rash keeps returning, or you think a medicine may be needed.
Every sign above is quoted from the sofidex article on Diaper rash. If you are not sure, err upward — it is always reasonable to be checked.