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 emergency help if you have difficulty breathing, cannot swallow your saliva, or develop rapidly increasing swelling of your tongue, lips, mouth, or throat.
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 same-day medical care if you cannot drink enough, are passing much less urine, feel unusually drowsy, or have other signs of dehydration.
You should also seek urgent advice for mouth sores accompanied by a widespread rash, blistering or peeling skin, eye pain, or sores around the genitals.
This is especially important after starting a new medicine.
Contact a clinician promptly if you have a weakened immune system and develop mouth sores with fever or feel generally unwell.
3
Does any of this apply?
Book an appointment
Book a routine appointment with a dentist or clinician if:
A sore lasts longer than three weeks
Sores repeatedly return or are becoming more severe
A denture, brace, filling, or sharp tooth keeps rubbing the area
You have unexplained weight loss, a neck lump, or trouble swallowing
There is a lasting red or white patch, lump, or thickened area
Every sign above is quoted from the sofidex article on Mouth sores. If you are not sure, err upward — it is always reasonable to be checked.