Clinical term

Allodynia

Allodynia is pain caused by a stimulus that is normally not painful: a light touch, the contact of clothing, gentle pressure. It is a descriptive clinical term: it describes what the person feels, without by itself designating a mechanism.

Scientific basis

The International Association for the Study of Pain (IASP) defines allodynia as pain due to a stimulus that does not normally provoke pain. Several forms are distinguished according to the stimulus involved: static mechanical, triggered by pressure; dynamic mechanical, triggered by rubbing or light touch; thermal, triggered by cold or heat.

Allodynia is observed in neuropathic pain, in migraine (where it is called cutaneous allodynia), in fibromyalgia and in other chronic pain conditions.

Depending on the situation, it may be associated with sensitization of nerve endings (peripheral sensitization) or with central sensitization. The IASP specifies that the term does not imply a mechanism: sensitization can only be inferred indirectly, from manifestations such as allodynia.

Blue Portance / SBNFA™ reading

A seat is first and foremost a support surface. In some people, a seated pressure that is usually painless becomes painful. In the SBNFA™ reading, allodynia is not the sign of a seat that is “too hard”: it indicates that a normally painless mechanical stimulus is now perceived as painful, without by itself identifying the mechanism involved. It is a reminder that pain when sitting cannot be reduced to the intensity of mechanical stress.

Contribution to the analysis of sitting

The observation focuses on tolerance of the points of support: where they are located, how long they are held, and whether they can be varied. Pain triggered by a seated pressure that is usually painless is useful functional information. It does not identify the mechanism involved or establish a diagnosis, both of which require a medical evaluation.

Not to be confused with

Hyperalgesia, increased pain in response to a stimulus that is already painful: allodynia concerns a normally painless stimulus, hyperalgesia a normally painful one; hyperesthesia, increased sensitivity to stimulation, a broader term; dysesthesia, an abnormal and unpleasant sensation, spontaneous or evoked; central sensitization, a neurophysiological mechanism that may be accompanied by allodynia, without allodynia being proof of it.

Sources and scope

An established clinical term (IASP). Its presence is not enough to identify a mechanism. This entry does not replace a medical evaluation.