Hi, I would like to know does hiv causes severe itchy scalp.

No. Typically "HIV dermatitis" is not itchy at all and usually located on the upper trunk (chest) and occasionally on the palms and soles. Since people who participate in high risk behavior can have other illnesses like syphllis or fungal skin infections which can be itchy, your best bet is to be tested. Usually when someone asks there is often high risk behavior. Don't put off testing!