Thank you for submitting your question.
I believe your son has a petechial rash. This type of rash is not itchy, and the lesions look like tiny red dots. They are flat and not raised.
Petechial rash can be a sign of low platelet count. Platelets are important in forming blood clots. When the platelet count is low, the person is prone to gum bleeding and bruising. He/she can also develop a petechial rash.
Low platelet count(thrombocytopenia) can be caused by medications, alcohol/drugs, or bone marrow disease. He should seek medical attention and have his platelet count checked.