Pain threshold

In a technical and medical literature the term pain threshold indicates the least stimulus which elicits pain (as reported by the subject) and is clearly differentiated from the term pain acceptance which indicates the degree of pain which a topic can tolerate before experiencing physical or emotional impairment and involves a measurement of a subject's response to pain. Compare this to absolute threshold, which is the lowest level of stimulus that is physiologically measurable.

Increased and decreased pain threshold

Pain threshold is frequently a function of how healthy the pain nerves and central pain processing pathways are, and of the chemical milieu in the tissues which the nociceptors innervate. It is commonly reduced by inflammation in the vicinity of nociceptors, such that normal touch becomes painful in the area of inflammation (allodynia). In such circumstances, the use of anti-inflammatory medications or physical therapies such as cooling or mild heat may return the nerve sensitivity or threshold to normal - it does not increase the threshold to above normal.

The use of morphine-like drugs does elevate the pain threshold (as well as pain tolerance). The same is true of a diverse number of other centrally acting analgesic drugs affecting pain relay neurons. Local physical techniques such as electrical stimulation, cooling or heat may temporarily increase the pain threshold.

However, short of damaging pain nerves - such as may occur in nerve injuries or neuropathies - the effects of interventions (pharmacological or physical) used to increase the pain threshold do not last much longer than the duration of their use. Additionally, in normal healthy persons, it is not significantly changed by any mental or physical practice or training. In contrast, pain tolerance may be increased by medications as well as by physical, cognitive and affective interventions and training.