Have you tried ALPHOSYL?? It is a tad stronger than Oilatum, available from all good chemists (personally recommend Boots) it can be found in the pharmacy section, not on the shelves with other cosmetic shampoo brands.
Also, after washing your kesh, air it out, I appreciate sometimes it takes hours for kesh to dry and we all have to rush off to work/school and so on, but when you're at home just open your kesh and let some air get through to your scalp.
Please try the ALPHOSYL 2 in 1 Shampoo (if you already have not), it is used for your condition - seborrhoeic dermatits.
Please let us know if it works.
All the best.