One way to tell is if your itch stops a few minutes after applying a good skin lotion/cream moisturizer like Cetaphil. If not, an evaluation by a Dermatologist is
in order to rule out fungal infection, or other issues.
Brain fog can be caused by a lot things; menopause, roller coaster glucose levels [highs then lows], depression, nutrient [mineral/s and/or vitamin/s] deficiency, junk foods, liver or kidney issues, cancer, and so on.