Often, the cause of Raynaud’s phenomenon is not known. Sometimes, it is a side effect of other conditions, such as connective tissue disease, trauma, or diseases of the glands or central nervous system. People with the disorder may feel numbness or tingling in their fingers and toes. They may also notice that their skin turns pale or blue, followed by reddening in the affected areas. Attacks may last from a few minutes to several hours and are usually treated with gradual warming of the fingers and toes to restore blood flow. Therapy may also include pain relievers, calcium channel blockers, quitting smoking, and avoiding cold temperatures and emotional upset.