Table of contents
Get treated by vein treatment industry leaders
What Causes Spider Veins?
Medically verified
Last updated on 1/29/2026
By Dr. Michael Nguyen
Vein Doctor at Vein Treatment Clinic
Harvard Medical School
Board Certified by the American Board of Venous and Lymphatic Medicine
Spider veins develop when small surface veins widen and become visible through the skin. Many patients notice them gradually and wonder why they formed in the first place.
In most cases, spider veins are not caused by a single factor. They usually develop due to a combination of genetics, hormonal influences, and pressure within the vein system.
Understanding what causes spider veins helps patients recognize risk factors, set realistic expectations, and decide when evaluation or treatment may be helpful.
If you’re unsure which factors may be contributing to your spider veins, a vein evaluation can help clarify the cause.
Genetics and family history
Genetics play a major role in spider vein development. People with family members who have spider veins are more likely to develop them.
Genetic causes of spider veins include inherited differences in vein structure and valve strength, which is why they cluster in families.
Spider Vein before and after treatment pictures.
Results may vary according to each case.
Spider Vein before and after treatment pictures.
Results may vary according to each case.
Hormonal changes
Hormonal fluctuations can weaken vein walls and contribute to spider vein formation.
This is why spider veins are more common during pregnancy, with birth control use, or during menopause.
Pregnancy-related vein pressure
Pregnancy increases blood volume and pressure in the leg veins while hormones relax vein walls.
Spider veins may improve after pregnancy, but underlying vein changes can persist.
Symptom Checker
Prolonged standing or sitting
Long periods of standing or sitting reduce the muscle action that helps move blood out of the legs.
Over time, increased vein pressure can cause small surface veins to dilate and become visible.
Sun exposure
Sun exposure spider veins are more likely on the face, where UV damage weakens tiny vessels near the skin, particularly on the face.
This damage makes spider veins more likely to appear in sun-exposed areas.
Aging and vein elasticity
As people age, veins naturally lose elasticity and strength.
Weaker vein walls are more likely to stretch and show through the skin.
Male, treated for varicose veins on the calves with VeinVanish™, a customized treatment plan tailored to his condition. The after photo shows the treated areas appearing smoother with the varicose veins visibly reduced.
Male, treated for varicose veins on the thighs and knees with VeinVanish™, a customized treatment plan tailored to his condition. The after photo shows the thighs and knees with a smoother-looking appearance.
Male, treated for varicose veins on the calves and knees with VeinVanish™, a customized treatment plan tailored to his condition. The after photo shows the affected areas appearing smoother-looking with the varicose veins visibly reduced.
Male, treated for varicose veins on the thighs, calves, and knees with VeinVanish™, a customized treatment plan tailored to his condition. The after photo shows smoother-looking legs with the varicose veins visibly reduced across the treated areas.
Male, treated for varicose veins on the calves and thighs with VeinVanish™, a customized treatment plan tailored to his condition. The after photo shows the legs appearing smoother-looking with the varicose veins visibly reduced.
Underlying vein pressure or reflux
In some cases, spider veins are linked to increased pressure from deeper vein reflux.
When underlying reflux is present, spider veins may recur unless the deeper issue is addressed.
Get the Facts on Chronic Venous Insufficiency. Read the Complete Guide
Do lifestyle factors cause spider veins?
Lifestyle factors such as inactivity, prolonged immobility, and excess weight can increase vein pressure.
While these factors may contribute, they are usually part of a broader set of causes rather than the sole reason spider veins form.