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
Any swallowed sodium hydroxide requires immediate advice from a poison centre and emergency medical assessment, even if there are no visible burns.
Call emergency services now if there is:
Trouble breathing, noisy breathing, or increasing throat swelling
Collapse, confusion, a seizure, or difficulty waking
Severe chest or abdominal pain
Vomiting blood or passing black, tar-like stool
A large, deep, or widespread skin burn
Sudden or worsening loss of vision
If the exposure was intentional, call emergency services and stay with the affected person if it is safe to do so.
Immediate medical and mental health support is important.
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
Eye exposure also needs immediate irrigation and urgent professional assessment.
Seek urgent help for coughing, wheezing, chest tightness, or breathlessness.
Contact the treating service promptly if swallowing becomes harder, food sticks, vomiting continues, weight is falling, a burn appears infected, or pain is getting worse.
3
Does any of this apply?
Book an appointment
After discharge, keep planned follow-up appointments.
The article also says
Move away from dust or mist into fresh air without entering an unsafe area.
Every sign above is quoted from the sofidex article on Sodium hydroxide poisoning. If you are not sure, err upward — it is always reasonable to be checked.