I will say you are allergy to some kind of food, nutrient or you have and internal parasite that is eating you up within your skin/blood stream
Itchy skin is not necessarily due to an allergy. It is a hallmark of liver disease, among other disorders. You need a full in-person work-up by a primary care physician.
Caregiver is correct.
Another cause can be very dry skin, if you are in a dry climate this could be a cause as well.
Where on your body is this itchy skin. It would be helpful to know.