What Causes Severe Itching Of Skin?

hello , i have a skin problem i think to be in total, i don t know where to start from but its not a dangerous problem i think , so i had this problem of an itchy skin , at night sometimes i scratch bad , but at day i am all normal , but when for example my blood get pumped up like running for 10 secondes or so , or moving lot , and also when the sun is a bit strong then i start feeling itchy in my skin and head and so, sometimes it makes me feel like stressed or so i dont know how to be specific , but that s almost all , to add also for example when am with friends or so and we make some laughs about each other and then about me when my blood pumped up again and face start getting red like shy or so then i start to get that itchy problem on my face and head again a bit. thank you in advance and i hope this website can help me , waiting for your advises and if should i should go to a doctor. sincerely