One thing I've become sure of is that needling sensation is usually part and parcel of a good treatment. The aim of a skilled practitioner is to create particular sensations and reactions in a patient, based on their situation. For example, if someone is weak and cold, the ideal sensation should be one of a spreading warmth. If there is an obstruction in a channel, there should be a sense of movement in that channel in order to re-establish proper flow, and so on. The idea that a point is 'good for headaches' for example, is I believe flawed. Any point will only bring about beneficial change if it is needled correctly, which involves deliberately attempting to elicit specific sensations, some of them quite strong.
In my experience patients will generally tolerate strong sensations happily if this is explained to them beforehand. The treatment process becomes more interesting and satisfying for both parties as particular reactions are sought through needle manipulation by the practitioner, and feedback from the patient.
Please note: this blog is intended for educational and general interest purposes only. If you have any health concerns, please discuss them with your doctor.