Pain Insensitivity (Reduced or Absent Pain Sensation)

Why pain insensitivity is dangerous

Pain makes you pull away from heat, stop walking on a broken bone and notice a stone in your shoe. Without it:

• foot ulcers form from pressure and rubbing in shoes
• burns occur from hot baths, heaters or hot water bottles
• fractures go unnoticed and heal badly
• joints are worn down by repeated small injuries (Charcot joints)
• infections spread before they are noticed
• in children, self-injury such as biting the tongue, lips and fingers

People with diabetic neuropathy are at high risk of foot ulcers, and foot ulcers are a leading cause of amputation.

Causes of pain insensitivity

Peripheral neuropathy

Damage to the long nerves of the limbs usually begins in the toes and feet and spreads upward in a "stocking and glove" pattern. People often feel numbness, tingling or burning, but some have loss of feeling only. Causes include:

• Diabetes: the most common cause. See diabetic peripheral neuropathy.
• Alcohol: heavy long-term use, often with nutritional deficiency.
• Vitamin B12 deficiency.
• Kidney failure, hypothyroidism and some cancers.
• Chemotherapy and other medicines.
• Inherited neuropathies such as Charcot-Marie-Tooth disease.

See peripheral neuropathy.

Spinal cord conditions

• Syringomyelia: a fluid-filled cavity in the spinal cord that disrupts the crossing pain and temperature fibers. It classically causes loss of pain and temperature sensation over the shoulders and arms in a "cape" pattern, while touch is preserved. People may notice painless burns on their hands.
• Spinal cord injury and compression.
• Multiple sclerosis and spinal cord tumors.

Brain conditions

Strokes affecting the brainstem or thalamus can reduce pain and temperature sensation on one side of the body or face.

Leprosy (Hansen's disease)

A treatable bacterial infection that damages skin and nerves. It causes patches of skin with reduced feeling and, later, numb hands and feet with injuries and deformity. It is rare in the US but still occurs in parts of Asia, Africa and South America.

Congenital insensitivity to pain

Rare inherited conditions present from birth:

• Congenital insensitivity to pain with anhidrosis (CIPA): no pain sensation and inability to sweat, causing fevers in hot weather.
• Congenital insensitivity to pain from SCN9A gene changes: no pain sensation with otherwise normal nerves, often with loss of smell.
• Other hereditary sensory and autonomic neuropathies.

Children may have tongue and lip injuries when teeth erupt, unnoticed fractures, joint damage and burns.

Temporary causes

• Local and general anesthetics, opioids and other strong pain relievers
• Intense stress or injury (the body's own pain-suppressing system briefly reduces pain)
• Severe cold
• Some psychiatric and developmental conditions, in which pain responses may be reduced or expressed differently

Distribution as a clue

How it is diagnosed

A doctor tests sensation to pinprick, temperature, light touch, vibration and joint position, and maps the area affected. A 10 g monofilament test on the soles is used to screen people with diabetes for loss of protective sensation. Further tests include:

• blood tests: blood sugar and HbA1c, B12, thyroid, kidney function, protein studies
• nerve conduction studies and electromyography
• skin biopsy to count small nerve fibers
• MRI of the spine or brain for central causes
• genetic testing for suspected inherited conditions
• skin smears or biopsy for leprosy

Treatment and protection

Treatment targets the cause: blood sugar control in diabetes, stopping alcohol, B12 replacement, treating leprosy with multidrug therapy, or surgery for syringomyelia or spinal cord compression. Nerve damage often does not fully recover, so protection is essential.

Foot and skin care

• Check your feet every day, using a mirror or asking someone to help. Look for cuts, blisters, redness and swelling.
• Wear well-fitting shoes and socks at all times, including indoors. Check inside shoes for stones before putting them on.
• Test bath water with your elbow or a thermometer; keep it below about 37 °C (98.6 °F) for bathing.
• Avoid hot water bottles, heating pads and sitting close to heaters.
• Keep skin moisturized but dry between the toes.
• Have toenails and calluses treated by a podiatrist.
• See a diabetes foot service at least yearly, more often if high risk.

For children with congenital insensitivity

Regular checks for injuries, protective equipment, dental care to prevent self-biting, careful temperature control in CIPA, and teaching the child and caregivers to recognize injuries without pain.

Frequently asked questions

What does it mean if you cannot feel pain?

It usually means the nerves that carry pain signals are damaged, most often by peripheral neuropathy from diabetes. Spinal cord problems, stroke, leprosy and rare inherited conditions are other causes. Because pain protects you from injury, loss of pain sensation should always be assessed.

What is congenital insensitivity to pain?

It is a group of rare inherited conditions in which a person cannot feel pain from birth. Affected children often have injuries, burns, fractures and bite wounds without noticing them. Some forms also prevent sweating. Management focuses on preventing and quickly treating injuries.

Why can't I feel pain in my feet?

The most common reason is peripheral neuropathy from diabetes. Other causes include heavy alcohol use, vitamin B12 deficiency, kidney disease and some medicines. See a doctor for tests, and check your feet daily for injuries you might not feel.

Is not feeling pain dangerous?

Yes. Without pain, injuries such as burns, blisters, cuts and fractures can go unnoticed and become infected or worsen. People with numb feet are at risk of ulcers and amputation. Daily checks, protective footwear and prompt treatment of any wound prevent most problems.