Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency medical help now if a child or teenager has repeated vomiting together with confusion, unusual behaviour, extreme sleepiness, difficulty waking, rapid breathing, a seizure, or loss of consciousness.
This is especially important during or soon after a viral illness.
Tell the emergency team about recent infections and all medicines taken, including non-prescription products.
Bring the packaging if it is available.
Do not wait for jaundice or other signs of liver trouble.
Reye syndrome can become severe without yellow skin or eyes.
Contact the follow-up team sooner if recovery seems to reverse or new symptoms develop.
After hospital discharge, routine follow-up is used to monitor liver recovery, neurological health, learning, behaviour, and rehabilitation needs.
The article also says
If a seizure occurs, protect the person from nearby hazards and place them on their side when possible.
Do not restrain them or put anything in their mouth.
Every sign above is quoted from the sofidex article on Reye syndrome. If you are not sure, err upward — it is always reasonable to be checked.