Symptoms of Erythromelalgia are listed as follows:
Erythromelalgia is characterized by severe, burning pain, marked redness (erythema) of the skin, swelling, and increased skin temperature, particularly of the feet. However, in some affected individuals, the hands may be the primary sites of involvement. Although both sides of the body are usually affected (bilateral), involvement may sometimes be limited to one side (unilateral), particularly in cases in which erythromelalgia has occurred secondary to another underlying condition or disorder (secondary erythromelalgia).

As noted above, disorder onset may sometimes occur gradually and subtly, possibly remaining relatively mild and unchanged in nature or degree over years or decades. However, in others with the condition, symptoms may begin suddenly (acutely) and, in some cases, may rapidly spread, increase in severity, and possibly become disabling over weeks. Reports suggest that, in many affected individuals, the disorder has a chronic course that may gradually increase in severity over time. In some with severe erythromelalgia, involvement may spread (usually bilaterally), such as from the feet up the legs (lower limbs), from the hands up the arms (upper limbs), from the upper to the lower limbs, from the lower to the upper limbs, or to the ears or face.

Associated symptoms may occur intermittently or on an almost continuous basis. Episodes or intensification of symptoms are sometimes described as "flaring", during which there is sudden (acute) redness, pain, sensation of heat, and swelling. During a flare, some affected individuals may also experience tingling pain or other symptoms similar to those associated with peripheral neuropathy. (For further information on this condition, please see the "Related Disorders" section of this report below.) Evidence suggests that, in many cases, flaring occurs late in the day and may last throughout the night, thus potentially interfering with sleep.

"Hallmarks" or characteristics of erythromelalgia include triggering or worsening of symptoms with exposure to heat (heat intolerance) or exercise and relief with cooling. These symptoms are characteristic of erythromelalgia but may occur with other disorders. They are not unique to erythromelalgia. The temperature at which symptoms may be triggered or exacerbated varies from person to person. (Please see the "Standard Therapies" section below for further information).