The following pain terminology is updated from "Part III: Pain Terms,
A Current List with Definitions and Notes on Usage" (pp 209-214) Classification
of Chronic Pain, Second Edition, IASP Task Force on Taxonomy, edited
by H. Merskey and N. Bogduk, IASP Press, Seattle, ©1994.
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Changes in the 2011 List
The work of the Task Force on Taxonomy in the era of 1979 to 1994 has
been continued by the Committee on Taxonomy that has worked to update
both pain terms and the classification of pain syndromes. All of the
terms have been carefully reviewed and their utility assessed in
reference to new knowledge about both clinical and basic science aspects
of pain. The Committee conducted its business primarily by e-mail, but
face-to-face meetings were held at each of the annual Congresses of
IASP. We now present the 2011 version of IASP Pain Terminology. Members
of the Taxonomy Committee in this era included: David Boyd, Michael
Butler, Daniel Carr, Milton Cohen, Marshall Devor, Robert Dworkin, Joel
Greenspan, Troels Jensen, Steven King, Martin Koltzenburg, John Loeser,
Harold Merskey, Akiko Okifuji, Judy Paice, Jordi Serra, Rolf-Detlef
Treede, and Alain Woda. The Chair would like to acknowledge the
continuous contributions that Harold Merskey has made to taxonomy since
the founding of IASP. As stated in prior publications of the IASP
taxonomy, we do not see this listing of terms as immutable. As we learn
more about pain, we will need to update terminology.
John D. Loeser, M.D.
Chair, IASP Taxonomy Working
Changes in the 1994 List Read 1994 Notes
There was substantial correspondence from 1986 to 1993 among members
of the Task Force and other colleagues. The previous definitions all
remain unchanged, except for very slight alterations in the wording of
the definitions of Central Pain and Hyperpathia. Two new terms have been
introduced here: Neuropathic Pain and Peripheral Neuropathic Pain.
The terms Sympathetically Maintained Pain and Sympathetically
Independent Pain have also been employed; however, these terms are used
in connection with syndromes 1–4 and 1–5, now called Complex
Regional Pain Syndromes, Types I and II. These were formerly labeled
Reflex Sympathetic Dystrophy and Causalgia, and the discussion of
Sympathetically Maintained Pain and Sympathetically Independent Pain is
found with those categories.
Changes have been made in the notes on Allodynia to clarify the fact
that it may refer to a light stimulus on damaged skin, as well as on
normal skin. Also, in the tabulation of the implications of some of the
definitions, the words lowered threshold have been removed from
the features of Allodynia because it does not occur regularly. Small
changes have been made to better describe Hyperpathia in the definition
and note. A sentence has been added to the note on Hyperalgesia to refer
to current views on its physiology, although as with other definitions,
that for Hyperalgesia remains tied to clinical criteria. Last, the note
on neuropathy has been expanded.
< Hide 1994
Introduction to the 1986 List Read 1986
A list of pain terms was first published in 1979 (Pain
1979;6:249–52). Many of the terms were already established in the
literature. One, allodynia, quickly came into use in the
columns of Pain and other journals. The terms have been
translated into Portuguese (Rev Bras Anest 1980;30(5):349–51),
into French (H. Dehen, Lexique de la douleur, La Presse
Medicale 1983;12(23):1459–60), and into Turkish (as Agri
Terimleri, translated by T. Aldemir, J Turkish Soc
Algology 1989;1:45–6). A supplementary note was added to these pain
terms in Pain (1982;14:205–6).
The original list was adopted by the first Subcommittee on Taxonomy
of IASP. Subsequent revisions and additions were prepared by a subgroup
of the Committee, particularly Drs. U. Lindblom, P.W. Nathan, W.
Noordenbos, and H. Merskey. In 1984, in particular response to some
observations by Dr. M. Devor, a further review was undertaken both by
correspondence and during the 4th World Congress on Pain of IASP. Those
taking part in that review included Dr. Devor, the other colleagues just
mentioned, and Dr. J.M. Mumford, Sir Sydney Sunderland, and Dr. P.W.
Wall. Following that review, it was agreed to take advantage of the
publication of the draft collection of syndromes and their system for
classification, to issue an updated list of terms with definitions and
notes on usage.
The versions now presented are based upon some subsequent discussions
by correspondence. The form of the definitions and notes at this point
has been the responsibility of the editor (H.M.). It would be difficult
now to single out individual contributions, but the editor remains
heavily indebted to those five members of the original Subcommittee on
Taxonomy who sustained this work in the form of an Ad Hoc group and
whose names are listed at the beginning of this report. Their knowledge
and patience was repeatedly provided freely and with good will.
The revised current list follows. The original comments provided as
an introduction to the terms are given in the following two paragraphs,
which indicate both the process by which the terms were first delivered
and the justification for them.
"The usage of individual terms in medicine often varies widely. That
need not be a cause of distress provided that each author makes clear
precisely how he employs a word. Nevertheless, it is convenient and
helpful to others if words can be used which have agreed technical
meanings. Following correspondence and meetings during the period
1976–1978, the present committee agreed on the definitions which follow,
and the notes have been prepared by the chairman in the light of
members' comments. The definitions are intended to be specific and
explanatory and to serve as an operational framework, not as a
constraint on future development. They represent agreement between
diverse specialties including anesthesiology, dentistry, neurology,
neurosurgery, neurophysiology, psychiatry, and psychology. A starting
point for some of these definitions was provided by the reports of a
workshop on Orofacial Pain held at the U.S. National Institute of Dental
Research in November 1974.
"The terms and definitions are not meant to provide a comprehensive
glossary but rather a minimum standard vocabulary for members of
different disciplines who work in the field of pain. We hope that they
will prove acceptable to all those in the health professions who deal
with pain. Not only are they a limited selection from available terms,
but it is emphasized that except for pain itself, they are defined
primarily in relation to the skin and the special senses are
excluded. They may be used when appropriate for responses to
somatic stimulation elsewhere or to the viscera. Except for Pain, the
arrangement is in alphabetical order."
It is important to emphasize something that was implicit in the
previous definitions but was not specifically stated: that the terms
have been developed for use in clinical practice rather than for
experimental work, physiology, or anatomical purposes.
< Hide 1986
Note: An asterisk (*) indicates that the term is
either newly introduced or the definition or accompanying note has been
revised since the 1994 publication.
An unpleasant sensory and emotional experience associated with actual or
potential tissue damage, or described in terms of such damage.
Note: The inability to communicate verbally does not negate
the possibility that an individual is experiencing pain and is in need
of appropriate pain-relieving treatment. Pain is always subjective. Each
individual learns the application of the word through experiences
related to injury in early life. Biologists recognize that those stimuli
which cause pain are liable to damage tissue. Accordingly, pain is that
experience we associate with actual or potential tissue damage. It is
unquestionably a sensation in a part or parts of the body, but it is
also always unpleasant and therefore also an emotional experience.
Experiences which resemble pain but are not unpleasant, e.g., pricking,
should not be called pain. Unpleasant abnormal experiences
(dysesthesias) may also be pain but are not necessarily so because,
subjectively, they may not have the usual sensory qualities of pain.
Many people report pain in the absence of tissue damage or any likely
pathophysiological cause; usually this happens for psychological
reasons. There is usually no way to distinguish their experience from
that due to tissue damage if we take the subjective report. If they
regard their experience as pain, and if they report it in the same ways
as pain caused by tissue damage, it should be accepted as pain. This
definition avoids tying pain to the stimulus. Activity induced in the
nociceptor and nociceptive pathways by a noxious stimulus is not pain,
which is always a psychological state, even though we may well
appreciate that pain most often has a proximate physical cause.
Pain due to a stimulus that does not normally provoke pain.
Note: The stimulus leads to an unexpectedly painful
response. This is a clinical term that does not imply a mechanism.
Allodynia may be seen after different types of somatosensory stimuli
applied to many different tissues.
The term allodynia was originally introduced to separate
from hyperalgesia and hyperesthesia, the conditions seen in patients
with lesions of the nervous system where touch, light pressure, or
moderate cold or warmth evoke pain when applied to apparently normal
skin. Allo means "other" in Greek and is a common prefix for
medical conditions that diverge from the expected. Odynia is
derived from the Greek word "odune" or "odyne," which is used in
"pleurodynia" and "coccydynia" and is similar in meaning to the root
from which we derive words with -algia or -algesia in
them. Allodynia was suggested following discussions with
Professor Paul Potter of the Department of the History of Medicine and
Science at The University of Western Ontario.
The words "to normal skin" were used in the original definition but
later were omitted in order to remove any suggestion that allodynia
applied only to referred pain. Originally, also, the pain-provoking
stimulus was described as "non-noxious." However, a stimulus may be
noxious at some times and not at others, for example, with intact skin
and sunburned skin, and also, the boundaries of noxious stimulation may
be hard to delimit. Since the Committee aimed at providing terms for
clinical use, it did not wish to define them by reference to the
specific physical characteristics of the stimulation, e.g., pressure in
kilopascals per square centimeter. Moreover, even in intact skin there
is little evidence one way or the other that a strong painful pinch to a
normal person does or does not damage tissue. Accordingly, it was
considered to be preferable to define allodynia in terms of the response
to clinical stimuli and to point out that the normal response to the
stimulus could almost always be tested elsewhere in the body, usually in
a corresponding part. Further, allodynia is taken to apply to conditions
which may give rise to sensitization of the skin, e.g., sunburn,
inflammation, or trauma.
It is important to recognize that allodynia involves a change in the
quality of a sensation, whether tactile, thermal, or of any other sort.
The original modality is normally nonpainful, but the response is
painful. There is thus a loss of specificity of a sensory modality. By
contrast, hyperalgesia (q.v.) represents an augmented response in a
specific mode, viz., pain. With other cutaneous modalities,
hyperesthesia is the term which corresponds to hyperalgesia,
and as with hyperalgesia, the quality is not altered. In allodynia, the
stimulus mode and the response mode differ, unlike the situation with
hyperalgesia. This distinction should not be confused by the fact that
allodynia and hyperalgesia can be plotted with overlap along the same
continuum of physical intensity in certain circumstances, for example,
with pressure or temperature.
See also the notes on hyperalgesia and hyperpathia.
Absence of pain in response to stimulation which would normally be
Note: As with allodynia (q.v.), the stimulus is defined by
its usual subjective effects.
Pain in an area or region which is anesthetic.
A syndrome of sustained burning pain, allodynia, and hyperpathia after a
traumatic nerve lesion, often combined with vasomotor and sudomotor
dysfunction and later trophic changes.
An unpleasant abnormal sensation, whether spontaneous or evoked.
Note: Compare with pain and with paresthesia. Special cases
of dysesthesia include hyperalgesia and allodynia. A dysesthesia should
always be unpleasant and a paresthesia should not be unpleasant,
although it is recognized that the borderline may present some
difficulties when it comes to deciding as to whether a sensation is
pleasant or unpleasant. It should always be specified whether the
sensations are spontaneous or evoked.
Increased pain from a stimulus that normally provokes pain.
Note: Hyperalgesia reflects increased pain on suprathreshold
stimulation. This is a clinical term that does not imply a mechanism.
For pain evoked by stimuli that usually are not painful, the term
allodynia is preferred, while hyperalgesia is more
appropriately used for cases with an increased response at a normal
threshold, or at an increased threshold, e.g., in patients with
neuropathy. It should also be recognized that with allodynia the
stimulus and the response are in different modes, whereas with
hyperalgesia they are in the same mode. Current evidence suggests that
hyperalgesia is a consequence of perturbation of the nociceptive system
with peripheral or central sensitization, or both, but it is important
to distinguish between the clinical phenomena, which this definition
emphasizes, and the interpretation, which may well change as knowledge
advances. Hyperalgesia may be seen after different types of
somatosensory stimulation applied to different tissues.
Increased sensitivity to stimulation, excluding the special senses.
Note: The stimulus and locus should be specified.
Hyperesthesia may refer to various modes of cutaneous
sensibility including touch and thermal sensation without pain, as well
as to pain. The word is used to indicate both diminished threshold to
any stimulus and an increased response to stimuli that are normally
Allodynia is suggested for pain after stimulation which is
not normally painful. Hyperesthesia includes both allodynia and
hyperalgesia, but the more specific terms should be used wherever they
A painful syndrome characterized by an abnormally painful reaction to a
stimulus, especially a repetitive stimulus, as well as an increased
Note: It may occur with allodynia, hyperesthesia,
hyperalgesia, or dysesthesia. Faulty identification and localization of
the stimulus, delay, radiating sensation, and aftersensation may be
present, and the pain is often explosive in character.
Diminished pain in response to a normally painful stimulus.
Note: Hypoalgesia was formerly defined as diminished
sensitivity to noxious stimulation, making it a particular case of
hypoesthesia (q.v.). However, it now refers only to the occurrence of
relatively less pain in response to stimulation that produces pain.
Hypoesthesia covers the case of diminished sensitivity to stimulation
that is normally painful.
|The implications of some of the above definitions may be
summarized for convenience as follows:|
and response mode differ
and response mode are the same
||raised threshold: increased response
and response mode may be the same or different
threshold: lowered response
||stimulus and response mode are the
The above essentials of the definitions do not have to be symmetrical
and are not symmetrical at present. Lowered threshold may occur with
allodynia but is not required. Also, there is no category for lowered
threshold and lowered response—if it ever occurs.
Decreased sensitivity to stimulation, excluding the special senses.
Note: Stimulation and locus to be specified.
Pain in the distribution of a nerve or nerves.
Note: Common usage, especially in Europe, often implies a
paroxysmal quality, but neuralgia should not be reserved for paroxysmal
Inflammation of a nerve or nerves.
Note: Not to be used unless inflammation is thought to be
Pain caused by a lesion or disease of the somatosensory nervous
Note: Neuropathic pain is a clinical description (and not a
diagnosis) which requires a demonstrable lesion or a disease that
satisfies established neurological diagnostic criteria. The term
lesion is commonly used when diagnostic investigations (e.g.
imaging, neurophysiology, biopsies, lab tests) reveal an abnormality or
when there was obvious trauma. The term disease is commonly
used when the underlying cause of the lesion is known (e.g. stroke,
vasculitis, diabetes mellitus, genetic abnormality).
Somatosensory refers to information about the body per se
including visceral organs, rather than information about the external
world (e.g., vision, hearing, or olfaction). The presence of symptoms or
signs (e.g., touch-evoked pain) alone does not justify the use of the
term neuropathic. Some disease entities, such as trigeminal
neuralgia, are currently defined by their clinical presentation rather
than by objective diagnostic testing. Other diagnoses such as
postherpetic neuralgia are normally based upon the history. It is common
when investigating neuropathic pain that diagnostic testing may yield
inconclusive or even inconsistent data. In such instances, clinical
judgment is required to reduce the totality of findings in a patient
into one putative diagnosis or concise group of diagnoses.
Pain caused by a lesion or disease of the central somatosensory nervous
system. See neuropathic pain note.
Pain caused by a lesion or disease of the peripheral somatosensory
nervous system. See neuropathic pain note.
A disturbance of function or pathological change in a nerve: in one
nerve, mononeuropathy; in several nerves, mononeuropathy multiplex; if
diffuse and bilateral, polyneuropathy.
Note: Neuritis (q.v.) is a special case of neuropathy and is
now reserved for inflammatory processes affecting nerves.
The neural process of encoding noxious stimuli.
Note: Consequences of encoding may be autonomic (e. g.
elevated blood pressure) or behavioral (motor withdrawal reflex or more
complex nocifensive behavior). Pain sensation is not necessarily
A central or peripheral neuron of the somatosensory nervous system that
is capable of encoding noxious stimuli.
Pain that arises from actual or threatened damage to non-neural tissue
and is due to the activation of nociceptors.
Note: This term is designed to contrast with neuropathic
pain. The term is used to describe pain occurring with a normally
functioning somatosensory nervous system to contrast with the abnormal
function seen in neuropathic pain.
An actually or potentially tissue-damaging event transduced and encoded
A high-threshold sensory receptor of the peripheral somatosensory
nervous system that is capable of transducing and encoding noxious
A stimulus that is damaging or threatens damage to normal tissues.
The minimum intensity of a stimulus that is perceived as painful.
Note: Traditionally the threshold has often been defined, as
we defined it formerly, as the least stimulus intensity at which a
subject perceives pain. Properly defined, the threshold is really the
experience of the patient, whereas the intensity measured is an external
event. It has been common usage for most pain research workers to define
the threshold in terms of the stimulus, and that should be avoided.
However, the threshold stimulus can be recognized as such and measured.
In psychophysics, thresholds are defined as the level at which 50% of
stimuli are recognized. In that case, the pain threshold would be the
level at which 50% of stimuli would be recognized as painful. The
stimulus is not pain (q.v.) and cannot be a measure of pain.
Pain tolerance level*
The maximum intensity of a pain-producing stimulus that a subject is
willing to accept in a given situation.
Note: As with pain threshold, the pain tolerance level is
the subjective experience of the individual. The stimuli which are
normally measured in relation to its production are the pain tolerance
level stimuli and not the level itself. Thus, the same argument applies
to pain tolerance level as to pain threshold, and it is not defined in
terms of the external stimulation as such.
An abnormal sensation, whether spontaneous or evoked.
Note: Compare with dysesthesia. After much discussion, it
has been agreed to recommend that paresthesia be used to
describe an abnormal sensation that is not unpleasant while
dysesthesia be used preferentially for an abnormal sensation
that is considered to be unpleasant. The use of one term
(paresthesia) to indicate spontaneous sensations and the other
to refer to evoked sensations is not favored. There is a sense in which,
since paresthesia refers to abnormal sensations in general, it might
include dysesthesia, but the reverse is not true. Dysesthesia does not
include all abnormal sensations, but only those that are unpleasant.
Increased responsiveness of nociceptive neurons to their normal input,
and/or recruitment of a response to normally subthreshold inputs.
Note: Sensitization can include a drop in threshold and an
increase in suprathreshold response. Spontaneous discharges and
increases in receptive field size may also occur. This is a
neurophysiological term that can only be applied when both input and
output of the neural system under study are known, e.g., by controlling
the stimulus and measuring the neural event. Clinically, sensitization
may only be inferred indirectly from phenomena such as hyperalgesia or
Increased responsiveness of nociceptive neurons in the central nervous
system to their normal or subthreshold afferent input.
Note: See note for sensitization and nociceptive neuron
above. This may include increased responsiveness due to dysfunction of
endogenous pain control systems. Peripheral neurons are functioning
normally; changes in function occur in central neurons only.
Increased responsiveness and reduced threshold of nociceptive neurons in
the periphery to the stimulation of their receptive fields.
Note: See note for sensitization above.
Last Updated: 22·May·2012