The exact cause of spider veins is still unclear but several factors can influence the onset. Such factors include: family history, hormonal changes, such as puberty and pregnancy, leg injury, prolonged standing, and being overweight. Birth control pills, or hormone replacement therapy also may trigger them. Spider veins arise more often in women because the female hormones are involved in their growth. Spider veins on the nose or cheeks may be triggered by excessive sun exposure. Sun protections is important to limit the number of spider veins on the face.