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 sneezing occurs with trouble breathing, wheezing, faintness, or swelling of the lips, tongue, face, or throat.
These may be signs of a severe allergic reaction.
If you have been prescribed an adrenaline auto-injector for severe allergies, follow your emergency plan.
A suspected button battery or strong magnet inside the nose needs immediate medical attention.
Do not try to remove it yourself.
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
Sneezing alone usually does not require urgent care.
Seek urgent medical advice after a significant chemical exposure, particularly if you also have breathing difficulty, chest tightness, severe eye irritation, or vomiting.
Move away from the fumes if you can do so safely.
3
Does any of this apply?
Book an appointment
Book a routine appointment if sneezing:
Continues for several weeks or keeps returning
Disrupts sleep, school, work, or daily activities
Does not improve after avoiding likely triggers
Occurs with ongoing facial pressure, reduced smell, or nasal blockage
Comes with one-sided, bloody, or foul-smelling nasal discharge
The article also says
A clinician can also help if over-the-counter treatments are not working or are causing unwanted effects.
Every sign above is quoted from the sofidex article on Sneezing. If you are not sure, err upward — it is always reasonable to be checked.