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 for breathing difficulty, swelling of the lips, tongue, or throat, collapse, or widespread hives after milk exposure.
These symptoms suggest an allergic reaction, not lactose intolerance.
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 prompt medical advice for:
Unexplained weight loss
Blood or black material in the stool
Persistent or severe abdominal pain
Fever, repeated vomiting, or diarrhea that does not settle
Symptoms that regularly wake you from sleep
Poor growth, feeding difficulty, or ongoing diarrhea in a child
Get urgent help if there are signs of severe dehydration, such as very little urine, marked drowsiness, confusion, fainting, or an inability to keep fluids down.
3
Does any of this apply?
Book an appointment
Arrange a routine medical appointment if symptoms keep returning, interfere with eating, or continue despite reducing lactose.
Assessment is also appropriate if you are unsure whether lactose is the trigger or need to remove major food groups.
Every sign above is quoted from the sofidex article on Lactose intolerance. If you are not sure, err upward — it is always reasonable to be checked.