There are a number of reasons why a broken blood vessel may occur. This could be due to;
Genetics – If broken blood vessels or thread veins are common in your family then you are going to be more prone to developing them too.
Age – As we become older, we come more at risk at developing broken blood vessels or thread veins as the collagen and elastin in the skin breaks down which causes the skin to become thinner and veins to become more noticeable.
Trauma – Injury or trauma to the skin can cause broken blood vessels to develop.
Medical Conditions – Certain medical conditions such as rosacea and liver disease can make you more likely to develop broken blood vessels.
Hormones – Hormonal changes such as puberty, menopause and pregnancy can cause spider veins to develop as body tries to adapt which is why women are often more susceptible to developing broken capillaries than men.