I have seborrhaeic dermatitis and have discovered that I can’t use anything with any kind of silicone. Most shampoos and styling products have them (especially conditioners) Silicones that are not soluble in water and build up on the hair: Cetearyl methicone, Cetyl Dimethicone, Cyclomethicone, Cyclopentasiloxane, Dimethicone, Dimethiconol, Stearyl Dimethicone, Amodimethicone (and) Trideceth-12 (and) Cetrimonium Chloride, and Trimethylsilylamodimethicone. Note: Trideceth-12 and Cetrimonium Chloride are only considered a silicone when both are combined with Amodimethicone. Some products claim to use water soluble silicones which are supposed to rinse clear, but my experience is very negative with these also. (Massive irritation) I have found solace with one product in particular which is unperfumed and sls/paraben/silicone free. It is called A’kin or Alchemy (they are the same company and seem to have a hard time choosing which name!!!)
alchemy unscented very gentle shampoo
I know it’s also available in the uk. It’s expensive, but it lasts for EVER!!! (Easily 4-5 months with daily use, collar-bone length hair.)
My hair was falling out in clumps around the irritated lumps and now it’s soft and thick and back to it’s healthiest. Oh, and the leave-in conditioner (which doesn’t touch your scalp) smells divine, and you use less than a pea-sized amount. It will last you years.