Telangiectases (spider veins) are permanently dilated superficial blood vessels. They may be capillaries, venules, or arterioles. They tend to increase in frequency and number with age, often due to actinic damage.

While telangiectases may be thought of as distinct clinical entities, they are also prominent features of certain diseases and may be clues to an underlying disorder. They can also be caused by medications, such as topical and oral steroids, as well as oral contraceptives.

Causes of telangiectases are many and include venous hypertension, local trauma, radiation damage, corticosteroid use, estrogen / progesterone excess, collagen vascular diseases, and multiple genodermatoses.

Telangiectases very rarely bleed. They are a cosmetic nuisance, and treatment is optional.