IASP Pain Terminology
The following pain terminology is 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, ©
IASP members: PDF version available in English and en Espãnol.
information on permission to use, reprint or translate any IASP
Changes in the 1994 list. There was
substantial correspondence from 1986 to 1993 among members of the Task
Force on Taxonomy 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 I-4 and I-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.
The 1986 list. A list of pain terms was first
published in 1979 (Pain, 6, 249-252). 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., 30, 5,  349-351,) into French
(H. Dehen, Lexique de la douleur, La Presse Médicale 12, 23, 
1459-1460), and into Turkish (as Agri Terimlëri, translated by T.
Aldemir, J. Turkish Soc. Algology, 1  45-46). A supplementary note
was added to these pain terms in Pain (14  205-206).
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 Oro-Facial 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
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.
Pain due to a stimulus which does not normally provoke pain.
Note: 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,
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 non-painful, 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
See also the notes on hyperalgesia and hyperpathia.
Absence of pain in response to stimulation which would normally
be painful. 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.
Pain initiated or caused by a primary lesion or dysfunction in
the central nervous system.
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.
An increased response to a stimulus which is normally painful.
Note: Hyperalgesia reflects increased pain on
suprathreshold stimulation. 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
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 are applicable.
A painful syndrome characterized by an abnormally painful
reaction to a stimulus, especially a repetitive stimulus, as well as an
increased threshold. Note: It may occur with allodynia,
hyperesthesia, hyperalgesia, or dysesthesia. Faulty identification and
localization of the stimulus, delay, radiating sensation, and
after-sensation may be present, and the pain is often explosive in
character. The changes in this note are the specification of allodynia
and the inclusion of hyperalgesia explicitly. Previously hyperalgesia
was implied, since hyperesthesia was mentioned in the previous note and
hyperalgesia is a special case of hyperesthesia.
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:
Allodynia: lowered threshold: stimulus and response mode differ
Hyperalgesia: increased response: stimulus and response mode are the
Hyperpathia: raised threshold: stimulus and response mode may be the
increased response: same or different
Hypoalgesia: raised threshold: stimulus and response mode are the same
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
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 pains.
Inflammation of a nerve or nerves. Note: Not to be used
unless inflammation is thought to be present.
Pain initiated or caused by a primary lesion, dysfunction, or
transitory perturbation in the peripheral or central nervous system.
Pain initiated or caused by a primary lesion or dysfunction in
the nervous system. Note: See also Neurogenic Pain and
Central Pain. Peripheral neuropathic pain occurs when the lesion or
dysfunction affects the peripheral nervous system. Central pain may be
retained as the term when the lesion or dysfunction affects the central
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. Neuropathy is not intended to
cover cases like neurapraxia, neurotmesis, section of a nerve, or
transitory impact like a blow, stretching, or an epileptic discharge.
The term neurogenic applies to pain due to such temporary
A receptor preferentially sensitive to a noxious stimulus or to
a stimulus which would become noxious if prolonged.
Note: Avoid use of terms like pain receptor, pain
A noxious stimulus is one which is damaging to normal tissues.
Note: Although the definition of a noxious stimulus has
been retained, the term is not used in this list to define other
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.
The least experience of pain which a subject can recognize.
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 Tolerance Level
The greatest level of pain which a subject is prepared to
tolerate. 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 which are unpleasant.
Peripheral Neurogenic Pain
Pain initiated or caused by a primary lesion or dysfunction or
transitory perturbation in the peripheral nervous system.
Peripheral Neuropathic Pain
Pain initiated or caused by a primary lesion or dysfunction in
the peripheral nervous system.