Thread veins are permanently dilated capillaries. These tiny capillaries have extremely thin walls, just one cell thick, that constantly dilate and constrict throughout our lives to help regulate body temperature.
However, contrary to popular belief, they are not ‘broken capillaries’.
Over time, these capillaries can lose their elasticity. As a result, they may not be able to constrict as efficiently, leading them to become permanently dilated. This is when they become visible through the skin, appearing as pesky thread veins, which we all hate, especially after a glass of red wine!