Chronic cold feet are most commonly the result of impaired circulation or lack of mobility. Impaired circulation, often associated with peripheral neuropathy, is a  symptom of many medical conditions 

Medical Conditions (inc. resource link)

• Muscular Dystrophy (MD)
• Arthritis
• Charcot Marie Tooth (CMT)
• Raynaud's
• Scleroderma
• Lupus
• Diabetes
• Multiple Sclerosis (MS)
• Cerebral Palsy
• Fybromyalgia
• Rheumatoid Arthritis
• Reflex Sympathetic Dystrophy (RSD)
• ...and other peripheral neuropathies

Applying direct heat to the feet can also help with relief from ailments and irritations

Ailments

• Foot Inflammation
• Insomnia
• Stress
• Tired & Achy Feet
• Dry & Flaky Feet
• Viruses
• Abrasions
• Calluses, Corns and Bunions