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 now if exposure is followed by:
Trouble breathing, severe chest pain, or blue or grey lips
Sudden confusion, weakness, vision loss, or trouble speaking
A seizure, collapse, or inability to wake
Severe or rapidly worsening abdominal pain
Vomiting blood
Significant swelling or burns of the mouth or throat
These symptoms may indicate a serious chemical burn, aspiration, or gas embolism.
And for anyone, someone who:
you believe has taken an overdose or swallowed something poisonous
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
2
Is any of this happening?
Be seen today
Contact a poison centre promptly after any swallowed hydrogen peroxide, particularly if the concentration is unknown or above ordinary household strength.
Do not wait for symptoms after swallowing a concentrated product.
After an eye splash, start rinsing immediately.
Urgent medical assessment is needed for ongoing pain, blurred vision, light sensitivity, or exposure to a concentrated product.
Seek urgent advice for blistering skin, a large exposed area, or pain that continues after rinsing.
3
Does any of this apply?
Book an appointment
Arrange routine follow-up after discharge if swallowing becomes more difficult, abdominal symptoms return, or recovery is not progressing as expected.
Every sign above is quoted from the sofidex article on Hydrogen peroxide poisoning. If you are not sure, err upward — it is always reasonable to be checked.