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 seizure lasts five minutes or longer, another seizure begins before the child recovers, or the child has trouble breathing.
Emergency help is also needed for blue or grey skin, severe breathing difficulty, marked unresponsiveness, or a rapidly spreading non-blanching rash.
A typical pink rash that appears as the fever ends, in a child who is alert and improving, is usually suitable for routine monitoring rather than emergency care.
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
Arrange prompt medical advice if the child’s fever lasts longer than expected, returns after improving, or is accompanied by worsening symptoms.
A baby younger than 3 months with a temperature of 38°C or higher needs urgent medical assessment.
Seek urgent medical care if the child:
Has their first seizure, even if it stops quickly
Is drinking very little or has signs of dehydration
Is unusually sleepy, difficult to comfort, or getting worse
Has a weakened immune system
Has a rash that is painful, blistering, or does not fade under pressure
Has fever with severe headache, neck stiffness, or repeated vomiting
Every sign above is quoted from the sofidex article on Roseola. If you are not sure, err upward — it is always reasonable to be checked.