I have seen this before when I was back working as a hairstylist for several years ago. This is a waxy type buildup that can happen usually seen in babies,and some adults. I've found that the only thing that seemed to work for me was to apply an oil such as Olive oil to the scalp massage it in really well leave in hair for about 20 minutes then use a fine toothed comb to gently loosen and remove the waxy build up. Then just low poo or use a co-wash using it 2X and rinse out apply leave in if needed. You need to be careful of how your applying product to your hair when cleansing/conditioning it. Apply a quarter to fifty cent size ammount of co-wash to wet hair and scalp. Then add to palms and rub together working from the back of the neck forward massaging and working it in good as you go.
I know using oil on your scalp for this sounds weird but the oil is what loosens the waxy build up. Its actually sebum or hair oils that are accumulating and bonding to conditioner/shampoo residue on the scalp. If this helps but it still needs more of it removed repeat the steps and maybe add a shampoo to remove chlorine or swimmers hair shampoo. This tends to be harsh and drying so you'll need to condition it well afterward. I'd recommend rinsing thoroughly from now on to help. Probably 1X a week ACV rinse after co-wash and before final rinse out. The ACV removes any residue and brings the ph level back to the hair. ACV works well as an occasional rinsing agent and PH level adjustor.
I hope this info helps~
3a/3bcurls, blonde, color treated,med fine.
Co-Wash: Suave Naturals & White Rain Conditioners,VO5 Moisture Milks, Burts Bees Super Shiny Grapefruit and Sugar Beet Shampoo
RO= GVPCB,Lustrasilk Shea Butter Cholestrol& Mango conditioner
LI= Herbal Essence Hello Hydration,VO5 Moisture Milks.
DT= JC WDT, GVP KPAK
Styling: FSG,,Ecostyler Krystal Gel, LALSG,
AfroVeda Curly Custard, Cocolatte Moisture Mask, Pur Whipped Gelly