Bulging veins aren’t always dangerous, but “they can sometimes indicate an underlying medical issue.” Common causes include aging, genetics, hot temperatures, tight clothing, exercise, sun exposure, and being overweight.

Veins bulge when blood pools in weakened or damaged veins instead of flowing smoothly to the heart. This can lead to varicose veins—“swollen, twisted veins that typically appear on the legs but can also show up on the arms.”

Some conditions can cause prominent veins, including phlebitis (vein inflammation), varicose veins, and deep vein thrombosis (DVT), a serious blood clot usually in the legs. Warning signs include “swelling or pain in the limbs,” skin discoloration, warmth, redness, or unusual vein patterns, especially on the chest or abdomen.

In uncommon cases, visible veins in the upper body may relate to liver or internal organ issues. If you notice other symptoms, “they are worth discussing with a medical professional.”

Seek medical advice if veins appear without reason, or if there’s pain, cramping, swelling, or skin changes. Most visible veins are harmless, but “if you notice anything unusual—or you’re unsure—it’s wise to talk to a healthcare provider.”