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 a product reaction causes trouble breathing, faintness, or swelling of the lips, tongue, or throat.
These may be signs of a severe allergic reaction.
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 medical care if a hair product or chemical treatment causes severe scalp pain, blistering, open skin, spreading redness, marked swelling, or discharge.
Rinse off the product according to its safety instructions and do not apply another chemical treatment.
3
Does any of this apply?
Book an appointment
Book a routine appointment if the dryness:
Does not improve after several weeks of gentler hair care
Starts suddenly without an obvious change in products or styling
Comes with substantial breakage, thinning, or bald patches
Occurs with fatigue, feeling cold, weight change, or skin changes
Develops alongside a very limited diet or concerns about nutrition
Is accompanied by persistent scalp itching, scaling, sores, or pain
These features do not identify a particular diagnosis.
They help show when it may be useful to look beyond ordinary hair damage.
Every sign above is quoted from the sofidex article on Dry hair. If you are not sure, err upward — it is always reasonable to be checked.