The classical prohibitions concern regions: the fontanelle in infants, the chest and back over the organs, the neck over the great vessels, and points that lie over a distended bladder or a full stomach. Modern practice adds the anticoagulated patient, the patient with a prosthetic valve or a bleeding disorder, and the infected site.
States as well as sites matter. Needling is deferred in acute febrile illness, after a heavy meal or alcohol, in extreme fatigue or hunger, and during pregnancy at points classically held to move qi strongly. These are not superstitions; each corresponds to a recognisable increase in risk.