CRPS (complex regional pain syndrome) feels like an intense, relentless burning in a limb, often described as if the affected hand, foot, arm, or leg is on fire from the inside. But the burning is only one layer. People with CRPS also report shooting, electrical, tearing, and squeezing sensations, frequently deep in the limb, sometimes feeling like the pain is coming from the bones themselves. The condition affects far more than just pain perception: it changes how your skin looks, how your limb moves, and how your body regulates basic functions like temperature and sweat.
The Burning and the Deeper Pain
Burning is the hallmark sensation of CRPS, so central to the condition that its older name, “causalgia,” literally means burning pain. But most people experience multiple pain types layered on top of each other. The surface of the skin can feel like it’s being stung or seared, while deeper in the limb there’s a persistent, heavy ache that many patients describe as bone-deep. These aren’t metaphors: research into the condition suggests that reduced blood flow to muscles and bone tissue produces real ischemic pain, the same kind of deep ache you’d feel if a tourniquet were cutting off circulation to your arm.
This deep aching pain tends to worsen with movement, which creates a difficult cycle. Moving the limb hurts, so you stop using it. But avoiding movement leads to stiffness, muscle wasting, and often more pain over time. Many people with CRPS develop a genuine fear of moving the affected limb, a psychological response called kinesiophobia that compounds the physical problem.
When Light Touch Becomes Unbearable
One of the most disorienting features of CRPS is allodynia, where sensations that should be completely painless become excruciating. A bedsheet brushing against your foot, a sleeve resting on your arm, a light breeze across your skin can all trigger sharp, disproportionate pain. This isn’t about being sensitive. The nervous system is genuinely misprocessing normal touch signals as danger.
Alongside allodynia, most people experience hyperalgesia, where things that would normally cause mild discomfort, like a pinprick or bumping your hand on a table, produce dramatically amplified pain. Together, these two features mean the affected limb feels like it exists in a constant state of threat. Even holding a coffee cup or resting your arm on a desk can be agonizing. The pain can be constant, intermittent, or spike suddenly when the limb is touched or used.
Skin That Changes Color and Temperature
CRPS isn’t invisible. The affected limb often looks noticeably different from the other side. Your skin may turn red, blue, purple, or blotchy white, sometimes cycling between colors throughout the day. The limb may feel distinctly warmer or cooler than the unaffected side. Early in the condition, the limb often runs warmer, but over time it tends to shift cooler, though this pattern varies from person to person.
Swelling is common, sometimes mild, sometimes dramatic enough that the limb looks puffy and tight. Sweating patterns can change too: the affected area may sweat excessively or barely at all compared to the other side. These visible changes aren’t cosmetic. They reflect genuine disruption to the blood vessels and nerves that regulate circulation, and they’re part of the formal diagnostic criteria for the condition.
Changes to Hair, Nails, and Skin Texture
Over time, CRPS can alter the physical structure of the affected limb in ways that feel alien. Hair on the limb may grow faster or thicker at first, then become thin or stop growing entirely. Nails may become ridged, brittle, or grow at unusual rates. The skin itself can change texture, becoming shiny and thin or thick and waxy. These “trophic changes” reflect ongoing disruption to the tissues that maintain normal growth and repair, and they tend to become more pronounced the longer the condition persists.
Some people also develop motor symptoms: tremors, muscle weakness, or dystonia, where muscles contract involuntarily and pull the limb into abnormal positions. A hand may curl inward or a foot may twist, making it physically impossible to use the limb normally even when pain levels are manageable.
Fatigue, Brain Fog, and the Whole-Body Impact
CRPS is often thought of as a limb problem, but it reaches far beyond the affected area. About 85% of people with CRPS experience clinically significant fatigue, and for two-thirds of them, that fatigue is severe. This isn’t ordinary tiredness. It’s a heavy, persistent exhaustion that doesn’t improve with rest, similar to what people describe with conditions like chronic fatigue syndrome or long COVID.
Roughly 65% of people with CRPS also report neuropsychological symptoms: trouble concentrating, memory lapses, and a foggy, detached feeling that makes it hard to think clearly. Some experience “neglect-like” symptoms, where the brain partially stops recognizing the affected limb as part of the body. You might struggle to locate the limb without looking at it, or it may feel foreign, as though it belongs to someone else. These cognitive and perceptual changes happen without any brain injury. They appear to be driven by the same nervous system disruption that causes the pain.
What Triggers Flare-Ups
CRPS pain fluctuates. Many people have a baseline level of discomfort that periodically spikes into intense flare-ups. Temperature is a common trigger: both warm and cold environments can intensify symptoms, though warm or hot weather is reported more frequently as a pain trigger. Research using whole-body thermal suits has confirmed this isn’t just perception. Warming the body and being upright (which increases blood flow to the lower limbs) measurably intensified pain, while cooling and elevating the limb provided relief.
Emotional stress, physical activity, and even changes in barometric pressure can all provoke flares. Because allodynia makes normal contact painful, everyday activities like getting dressed, showering, or being in a crowded space where someone might brush against you can escalate symptoms quickly.
When Pain Spreads Beyond the Original Site
CRPS typically stays in one limb, but it can spread. In a study of 72 patients whose CRPS moved to a second limb, the most common pattern was contralateral spread (53%), meaning it jumped to the same limb on the opposite side, from one hand to the other or one foot to the other. About 32% experienced ipsilateral spread, moving from an arm to a leg on the same side or vice versa. Diagonal spread, like right hand to left foot, was rare (15%) and almost always followed a new injury to that limb.
When spreading happens without a new injury, it most often follows the contralateral pattern, with 63% of spontaneous spread cases jumping to the mirror limb. This is thought to involve changes in how the spinal cord and brain process pain signals, essentially a central nervous system problem rather than a local tissue problem. For people living with CRPS, the possibility of spread adds another layer of anxiety to an already overwhelming condition.