Spider veins can most commonly be found on the face and legs. Vascular lesions such as birthmarks, rosacea, spider veins, varicose veins, and telangiectasias arise from a wide range of natural and environmental sources:

Weight Gain
Weight
Hereditary
Pregnancy
Hormonal
Birth Control Pills
A history of blood clots
Exposure to UV rays
Crossing legs
Standing for extended periods
Trauma or impact, such as regular running or jogging or any sport activity

Treatment of veins depends on the principle of selective photothermolysis; the laser light is applied, and the light energy is absorbed by the chromophore (in this case hemoglobin) and converted to heat which breaks up coagulated blood. Surrounding tissue remains undamaged.
Laser vein therapy is also the treatment of choice for spider veins that are impossible to inject because they are too small.
In many cases several sessions are required to maximize results, but you can see improvement after only one session.

The results of laser treatment for spider veins are not immediate. After laser therapy the vessels underneath the skin will gradually change from a dark blue to light red color then eventually disappear in three to six weeks.

Post Laser Vein Treatment, some redness or bruising may occur. Most experience little to no pain.