I believe it is limited amount of platelets lots of things can contribuit to this one of them is drinking alcohol it is actually bleeding under the skin ,Iwould suggest seeing your doctor and maybe takin some vein strenthening vitamins such as horse chesnut supplement (you can get from the likes as holland and barret) there are also others available if you ask in there they will look things up for you they were very good I also had this when I came off my holiday flight last year so cabin pressure may have something to do with this and week veins,hopoe this helps,su.
