The most common cause of bulging veins when talking is tension in the surrounding neck muscles pushing the veins out toward the skin surface, according to Sing Wise. These veins are more visible in people who have less subcutaneous fat, notes Scientific American.
Subcutaneous tissue forms the second layer of skin underneath the epidermis, according to About.com. This layer of tissue contains larger blood vessels, and the overall size of this layer varies per person. People with more fat in their subcutaneous layer are less likely to have bulging veins when talking or exercising because those veins are more insulated and harder to see. When a muscle hardens or contracts, the nearby veins get flattened up against the surface of the skin and appear to bulge, explains Scientific American.
People with bulging veins in their necks have tense muscles in the neck area when they speak, but this should not result in any health problems, according to Scientific American. The bulging veins are neither a positive nor a negative occurrence, and are simply the result of individual physiology. The same phenomenon occurs in the arms and legs of some people during strenuous exercise. The veins disappear again once the surrounding muscles return to a relaxed state.