Spider nevi may appear as red rash, but in fact these reddish lesions consist of dilated subcutaneous blood vessels. They occur because of hormonal imbalances associated with poor liver function. Liver degrades hormones including female sex hormone estrogen. Estrogen is created in bodies of both sexes and its concentration increases disproportionately in cirrhotic patients. This may lead to enlargement of breast tissue in males (called gynecomastia). In addition, estrogen causes dilation of blood vessels and in skin this manifests by spider nevi presence.
As mentioned above, spider nevi are typical for liver cirrhosis associated with chronic liver failure. However, sometimes spider angiomas occur by people with healthy liver, especially by women in conditions associated with elevated levels of estrogen like during pregnancy or when using hormonal contraceptives.
Spider nevi are visible by naked eye. They are usually located on face, upper limbs and upper torso. They only rarely appear on body surface below level of navel.
In otherwise healthy humans, spider nevi are often temporary, in pregnancy they usually resolve after delivery, in users of hormonal contraception angiomas disappear after its withdrawal. In cirrhotic patients spider nevi occur in large quantities and tend to be permanent. If someone is interested, spider nevi can be treated with laser with only a small risk of minor scars.