Being overweight and child bearing tend to worsen spider veins. Spider veins are more common in women and become more numerous with age. The reason these veins stretch is not known. Trauma to an area can cause spider veins to form. There is no reliable means of prevention.
Spider veins are harmless.
The only reason for treatment is strictly cosmetic. Sclerotherapy is one of the most successful therapies available for removing spider veins. Sclerotherapy involves injecting a solution through a very tiny needle into the veins. This causes irritation and inflammation inside the vessel and leads to closure of the vessel. With no blood flowing, the veins become invisible and are replaced by scar tissue.