Have you tried a co-wash with mint in it? I find mint/menthol really soothes my scalp. I know some type of mint/menthol is in DevaCurl No-Poo, Curl Junkie Daily Fix, and Queen Helene Mint Julep (a low-poo), because I buy them specifically for the cooling sensation!
A product that helps me with itching any time/place is Hawaiian Silky Miracle Worker 14-in-1 Spray. (Yes, the name is ridiculous). I spray it on my hair and leave it under my sleep cap all night, and it soothes any itchies. It also makes my hair really soft and smooth. It has both chamomile and menthol, which feel so good on the scalp, but, unlike a cleanser, it can be used at any time. You can spray it or rub right on itchy spots and it works immediately.
I also use pure jojoba oil, rosewater and glycerin, and witch hazel on my scalp, depending upon the severity of the itches and the condition of my hair. (If my hair is dry, I avoid the witch hazel because it's so astringent.) For me, the mint/menthol helps the most, though.
3b, Coarse, Low Porosity, Desert ClimateFavorites: CK Knot Today, Mystic Divine Shampoo, Conditioner & Curl Cream, Miracle 7 Heavenly Healer Shampoo & Leave-in, Miss Jessie's Quick Curls, Ouidad Climate Control Gel