Why do your thumbs go numb when you are cold?

The human body's response to cold temperatures involves several mechanisms to conserve heat. One of these mechanisms is vasoconstriction, where the blood vessels narrow, reducing blood flow to the extremities, such as the fingers and thumbs. This helps to conserve heat in the body's core.

When the body is exposed to cold temperatures, the blood vessels in the hands and feet constrict to reduce heat loss. This constriction can compress the nerves that supply sensation to the thumbs, causing them to feel numb.

In severe cases, the numbness in the thumbs can be accompanied by other symptoms, such as tingling, pain, or discoloration of the skin. These symptoms may indicate a more serious condition called frostbite, which requires immediate medical attention.

To prevent numbness in the thumbs and other extremities during cold weather, it is important to wear warm clothing, including gloves and mittens. Hand warmers or chemical heat packs can also be used to provide additional warmth to the hands and fingers.