Unexplained symptoms are worth exploring, but it's important to first speak to your GP and have potential medical causes appropriately investigated. This library is for information only and does not replace medical advice, diagnosis or testing.
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Chronic pain, also known as persistent pain, describes pain that continues or recurs for longer than three months.
Unlike acute pain, which often occurs in response to an injury or illness and gradually settles as the body heals, chronic pain can continue long after an initial injury has resolved. It can also develop without an identifiable injury or obvious cause.
Pain can take many forms, including aching, burning, stabbing, throbbing, tingling, pressure, tightness or electric shock-like sensations.
For some people, pain is concentrated in one area of the body. For others, it is widespread, moves between different locations or changes in character over time.
Chronic pain can occur alongside conditions such as fibromyalgia, ME/CFS, Long COVID, arthritis, neuropathy, migraine and other chronic illnesses.
It may be constant or intermittent, predictable or seemingly random. Its intensity can range from mild background discomfort to severe, disabling pain.
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Pain is a complex sensory and emotional experience involving the nervous system, brain and body.
It is not simply a direct measurement of tissue damage. Instead, pain emerges through interactions between sensory information, the nervous system and the brain's interpretation of that information.
Pain Signals and the Nervous System
The body contains specialised sensory nerve endings called nociceptors, which detect potentially harmful stimuli such as extreme temperatures, pressure or chemical changes associated with tissue injury.
These signals travel through nerves and the spinal cord to the brain, where they contribute to the experience of pain.
However, pain can also occur without ongoing tissue damage, and tissue damage does not always produce pain.
This distinction is particularly relevant to persistent pain conditions.
Different Types of Pain
Pain is commonly described in three broad categories, although these can overlap.
Nociceptive pain: Pain associated with actual or threatened damage to non-neural tissues, such as muscles, joints or other body structures.
Neuropathic pain: Pain caused by a lesion or disease affecting the somatosensory nervous system. It may feel like burning, shooting, tingling or electric shocks.
Nociplastic pain: Pain associated with altered pain processing, where pain occurs despite no clear evidence of tissue damage sufficient to explain it or a lesion or disease of the somatosensory system causing the pain.
These categories describe different processes rather than how severe or genuine someone's pain is.
Nervous System Sensitivity
The nervous system continuously processes information from the body.
In some persistent pain conditions, pain-processing pathways become more responsive to sensory input.
This is sometimes described as sensitisation.
Two related experiences are:
Hyperalgesia: An increased pain response to something that would normally be painful.
Allodynia: Pain caused by something that would not ordinarily be painful, such as light touch or clothing against the skin.
This can help explain why relatively minor sensations may become intensely uncomfortable.
Sensitisation is one possible contributor to persistent pain, but it does not explain every pain condition.
The Brain's Role in Pain
The brain integrates sensory information with other processes, including attention, memory, emotion and previous experiences.
This means pain is influenced by more than signals arriving from a particular part of the body.
For example, pain may become more noticeable when someone is exhausted, distracted by discomfort or experiencing heightened physiological arousal.
Stress and emotional experiences can influence pain intensity, but this does not mean that persistent pain is psychological or caused by repressed emotions.
Pain remains a real experience regardless of whether a clear structural explanation has been identified.
Pain Without an Obvious Injury
One of the more confusing aspects of persistent pain is that it may occur without a recognisable injury or clear relationship to physical activity.
Some people experience pain that changes location, appears suddenly or feels different from one episode to another.
Pain can also continue after an injury has healed, reflecting ongoing changes in the tissues, nervous system or pain-processing pathways.
The absence of an obvious injury does not mean that the pain is imagined or insignificant.
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The nervous system has an important role in detecting potential threats and helping the body respond to danger.
When the brain perceives a threat, the body's stress response can increase alertness, muscle tension and sensitivity to physical sensations. This is sometimes described as being in survival mode.
These responses are designed to protect us. However, when the body's threat-response systems remain highly activated, they can contribute to increased pain sensitivity.
For some people living with persistent pain, the nervous system may become more responsive to signals that it interprets as potentially threatening, even when there is no ongoing injury.
This can mean that ordinary movement, pressure or physical sensations become uncomfortable or painful.
Pain itself can also be experienced as a threat, creating a cycle in which pain increases alertness and heightened alertness makes pain more noticeable or intense.
Stress, Emotions and Pain
The systems involved in processing pain also interact with those involved in stress and emotional regulation.
Periods of prolonged stress, anxiety or emotional strain can influence pain sensitivity, muscle tension and the intensity of pain.
Some people also notice connections between their pain and difficult emotional experiences, including emotions they may not have fully recognised or expressed.
However, these relationships vary considerably. There is no established evidence that repressed emotions are a universal cause of chronic pain, and many persistent pain conditions involve identifiable physical or neurological processes.
Importantly, survival mode is a way of describing heightened protective responses, not a formal medical diagnosis or an explanation for every type of chronic pain.
The key distinction is that pain can be influenced by the body's protective systems without being imaginary, consciously produced or necessarily caused by psychological distress.
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Pain doesn't always mean something is being damaged.
Pain is influenced by the nervous system and does not always correspond directly to the presence or extent of tissue injury.
Chronic pain can exist without a clear diagnosis.
Some people experience persistent pain despite investigations not identifying a specific structural cause.
Pain can move around the body.
The location, intensity and character of pain may change, sometimes without a recognisable pattern.
Different types of pain can feel similar.
Burning, aching, stabbing or tingling sensations may arise through different processes. The sensation alone does not necessarily identify the underlying cause.
Pain can fluctuate significantly.
Someone may experience relatively mild discomfort one day and severe pain the next, without an obvious explanation.
Pain and fatigue often overlap.
Persistent pain can coexist with exhaustion, sleep disturbances, cognitive difficulties and other symptoms.
Pain is both sensory and emotional.
The emotional dimension of pain is part of how humans experience it. This does not mean pain is imaginary or that emotional distress must be its cause.
Pain can be invisible.
A person may appear physically comfortable while experiencing significant pain that affects their concentration, movement or ability to participate in everyday activities.
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Persistent pain can be difficult to describe, particularly when it changes or doesn't follow a recognisable pattern.
The constant background ache: Experiencing discomfort that remains present throughout the day, even when its intensity changes.
The sudden stabbing pain: Feeling sharp or intense bursts of pain that appear unexpectedly.
The burning sensation: Experiencing heat, burning or stinging without an external source of heat.
The electric shock: Feeling brief, shooting or shock-like sensations in different parts of the body.
The moving pain: Noticing discomfort in one area that later disappears or emerges somewhere entirely different.
The painful touch: Finding clothing, bedding, pressure or ordinary contact uncomfortable.
The unpredictable flare: Experiencing a significant increase in pain without an obvious injury or identifiable event.
The deep internal ache: Feeling pain that seems to originate from deep within the body rather than from the skin or surface tissues.
The invisible experience: Continuing conversations or everyday activities while managing significant discomfort that others cannot see.
For some people, pain remains relatively consistent in location and sensation. For others, it can be one of the most unpredictable aspects of chronic illness.
The same person may experience aching, burning, stabbing or pressure sensations at different times, sometimes in completely unrelated areas of the body.
This variability can be confusing, particularly when pain appears without a clear physical explanation or changes faster than someone can make sense of it.
Persistent pain can also affect sleep, concentration, emotional wellbeing, mobility, relationships and everyday independence.
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Persistent pain can be associated with a wide range of health conditions, including inflammatory disorders, neurological conditions, musculoskeletal problems and changes in pain processing.
New, worsening or unexplained pain may warrant medical assessment, particularly when accompanied by other new symptoms or changes in physical functioning.
Sudden severe pain, chest pain, significant neurological changes, or severe back pain accompanied by new bladder or bowel dysfunction or numbness around the groin can indicate a medical emergency.
