When you suffer from a condition known as purpura, blood vessels anywhere within your body actually begin to leak, causing purplish spots to develop along your skin. It is essentially an issue involving the ability of your blood to coagulate. When you have this condition, your blood does not clot as it would normally, triggering a leakage of blood from your capillaries that pools just under your skin. As with almost any disorder that can affect your body, a number of contributing factors can cause this condition.
For some people, the condition's actual cause is unknown. Certain capillaries, most often those found in the lower half of your body, such as your buttocks, legs and feet, simply leak blood that eventually develops the "hallmark" patches associated with this condition. However, the lack of an underlying or discernible cause does not negate the ability to treat purpura. Most people with this form of condition respond favorably to prescription medications, like corticosteroids and immune globulin, to increase the platelet count of the blood.
Abnormal Immune Response
For others, purpura is directly linked to an abnormal immune response, meaning that the body actually begins to target healthy platelets your system. Antibodies that normally attach themselves to foreign pathogens, marking them for destruction, begin to adhere to your platelets. As the amount of platelets drop in your blood, the blood's ability to coagulate or clot greatly diminishes, which can lead to the leakage of this fluid from your capillaries.
It is also quite possible for purpura to manifest out of an infection. In this situation, a bacteria or virus that infects the body can cause an adverse reaction from your immune system that prompts an inflammation within the blood vessels. This may cause the affected vessels to bleed, forming purplish patches along the skin.
Sometimes, both prescription and nonprescription medications can trigger purpura in certain individuals. Antibiotics are probably one of the more common culprits, but you may also develop this condition from antihistamines or vaccinations. And much like in the case of infections, the active ingredients found in some medications can cause an inflammation within the blood vessels, prompting them to bleed.
Though not necessarily as common as other causes of this condition, purpura may also spin out of drastic temperature changes, especially when it comes to the cold. When your skin is exposed to an extreme drop in temperature, the capillaries may begin to swell. As they become engorged with blood, some of it may leak out, triggering the condition and formation of purple patches on the skin.
Insect bites, like those from bees, flies or mosquitoes, can also trigger an inflammation of the blood vessels associated with the condition. This may prompt some bleeding from your capillaries and the development of discolored patches along the skin.