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
Emergency care is appropriate for confusion, fainting, trouble breathing, severe weakness, rapidly worsening illness, or signs of shock.
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
Seek same-day or prompt medical care if:
The boil is on the face, near an eye, or inside or near the nose.
Pain, swelling, or redness is rapidly worsening.
Redness is spreading away from the boil.
Fever, chills, red streaks, or swollen lymph nodes develop.
There are several boils or a large carbuncle.
The person has diabetes, poor circulation, or reduced immune defenses.
A young infant has a boil or other suspected skin infection.
Symptoms worsen after drainage or while taking prescribed treatment.
3
Does any of this apply?
Book an appointment
Arrange routine follow-up if the boil is not improving after several days of careful home treatment, has not healed within about two weeks, or keeps returning.
A clinician should also review ongoing drainage, a wound that will not close, or a lump that repeatedly develops in the same location.
The article also says
After professional drainage, attend any recommended wound checks.
Contact the treating clinician if the dressing becomes soaked repeatedly, bleeding does not stop with gentle pressure, pain becomes much worse, or new fever develops.
To lower the chance of spread or recurrence, keep healing wounds covered, wash hands regularly, clean shared equipment, avoid sharing personal items, and shower after close-contact sports.
Household members with painful or draining skin lesions should seek their own medical advice rather than sharing medicines.
Every sign above is quoted from the sofidex article on Boils. If you are not sure, err upward — it is always reasonable to be checked.