I get places like that with my seborrheic dermatitis, too. Psoriasis can also cause them. This is why I can't go strictly CG and have to low-poo occasionally with Giovanni Tea Tree Triple Treat Shampoo - much better results than with Paul Mitchell Tea Tree Shampoo, which is undesirable to most because it contains sulfates, unless it's recently been reformulated. My hair just otherwise prefers the natural ingredients in the Giovanni, too.

And when I co-wash, I use the matching conditioner, applying it and working it into my scalp for several minutes before ever getting into the shower. I leave it on for 10-15 minutes when I have time.
2C/3A/3B - mod. CG, med. to fine, normal to low porosity/normal elasticity

Current Main Rotation: MG217 medicated, GTTT or Aim2Health 'poos as scalp needs, YTCarrots or Elucence cond., Spiral Solutions Protein Trtmt & Deeply Decadent Cond., CJCCCC reg or lite, KCCC, AO Mandarin Magic, Giovanni LA Hold Hair Spritz + lots more, sporadically

HG Method: Super Soaker + Smasters-ing, brief upside down diffusing then clips or clamps & air dry. Blend gray w/henna glosses