Sometimes, bulging veins can be a sign of a health problem, but they aren’t always dangerous. Knowing why veins become more visible is important for knowing when to see a doctor.

Too much exercise, getting older, hot weather, tight clothes, genetics, being in the sun, and being overweight are all common causes. They are usually not dangerous, but you should see a doctor if your veins change color.

Bulging happens when blood doesn’t flow smoothly back to the heart and instead collects in weak or damaged veins. This can cause varicose veins, which are swollen, twisted veins that are most common in the legs but can also be found in the arms.

The  Cleveland Clinic says that smoking, being overweight, genetics, hormonal changes (especially during pregnancy), and standing or sitting for long periods of time are the main causes of varicose veins.

The treatment depends on how bad it is. Doctors may suggest injection therapy, raising the legs, wearing  compression stockings, or, in more serious cases, vein surgery.

Varicose veins can lead to venous ulcers, which are slow-healing open wounds near the ankles that happen when blood doesn’t flow properly.

They can also raise the chance of blood clots, which can cause pulmonary embolism, superficial thrombophlebitis, or deep vein thrombosis, all of which need immediate medical attention.

Regular exercise, keeping a healthy weight, quitting smoking, and wearing loose clothing, especially around the waist, can lower the risk of varicose veins, but they can’t always be avoided.