In Great Britain it is illegal to make a medical diagnosis unless you are a qualified and licensed doctor, or a veterinary surgeon. Spiritual healers are not usually trained as doctors - though some might be.
Many patients are emotionally vulnerable, particularly if they’ve sought a healer’s help after the medical profession has given up all hope of them making a recovery.
The healer’s spirit guides can see patients’ physical ailments reflected in their auras, and they'll do their best to treat them appropriately.
On a cautionary note:
Practicing professional healers of all kinds need adequate insurance cover, usually obtained via their regulatory or training organisations.
If someone makes an allegation of misconduct against a healer, and the case proceeds to court, legal costs will need to be covered (see Contacts).