Is petechiae dangerous?

Hannah

So I think from the beginning of the year I started getting one or two little pin point red dots on my arm. But within the last two months I’ve noticed I’ve been getting more and more and now they are on my legs too. I’ve looked it up and all I’m getting are they are cause by blood disorders which I don’t have, leukemia which I don’t think I have. Can they just show up without cause or should I worry?