Pigmentation caused by scratching due to recurring itching. What is the cause?

Every year during the transitional seasons of autumn and spring, I suffer from unbearable skin itching. Although it is mild during the day, the itching intensifies at night, causing me to scratch unconsciously. This leaves dark pigmentation in those spots, which is unsightly.

Even applying a generous amount of moisturizer only provides temporary relief, and I am worried that my skin is becoming increasingly rough due to the wounds caused by scratching. I would like to hear the exact cause from someone who provides meticulous care like Dr. Jung Da-jeong; I am curious whether it is simply due to dryness or if it is a symptom of another allergy. Please advise on practical measures to soothe the itching without leaving scars, or if there are any ointments I can be prescribed.