Our experience with eczema and seborrheic dermatitis... but as pointydogg writes, each case is different.
a. natural oils made it worse; vaseline/mineral oils (I know... people don't like them for babies, but it was better than the pus-infected skin which was exarcebated by natural oils) to loosen flakes off. One idea is that natural oils may be used by bacteria/fungi as a nutrient source. Shea butter works for some people (skin); DD was a red rash afterwards.
b. keep the skin clean - wash and moisturise. At first we were doing this three times a day and washing hair twice a day to keep the scalp clean (we were putting a cloth down at night and changing it 3-4 times during the night, just to give you an idea of how weepy her skin was).
c. swaddling - up to 10 months, at which time she kept 'breaking out' of her swaddling. Yes, it was tight but I would rather that than a bloodbath. Better not to start the scrathing cycle than try to break it.
d. as she got older, we used socks on her hands as scratch mitts were too small. Mitts/socks - can still buff skin but at least less damage than scratching.
e. if the skin looks infected, get antibiotic cream from the dr. It will make a huge difference.
f. Aveeno was not good for us. Turns out she has milk allergy and there is milk protein in Aveeno and she was likely reacting to this. I shudder to think of how much of it got rubbed in and I didn't realise I was making things worse.
g. keep a food diary (yours too if she is BF) and a diary of her symptoms as well. It may take a few weeks but it will help you recognise any trends. Might want to include details of how you are treating her skin/scalp too. This was invaluable when we got sent to the paediatrician, dermatologist and allergist; they appreciated having so much history and knowledge accumulated.
h. be patient. It may take a while to figure out. It has taken us two years but her skin looks normal now!
i. be prepared to try different things e.g. ways of handling eczema, and different creams.
j. we found Weleda best for her scalp and washing her skin when it was very icky. Otherwise, bath is just water although did use Oilatum at one point and found this good. As she has gotten older, we started to use Spectro Kids and it has nipped the last bit in the bud (wash her once a day with the liquid soap, moisturise after bath at night and first thing in the morning. At height of eczema, moisturising every nappy change +). Must add though that eczema is under control as it is food related and she is on a strict diet (milk and egg very bad).
k. don't do exclusion diets unless your diary suggests a very good reason for it. If you do, be ruthless and make no exceptions. Plan meals in advance!
l. come to MN!
Good luck! I can remember how hard and soulbreaking this is... I look at pictures taken on a 'good' day and am horrified. The turning point was when I was BF and watching pus ooze out from under her scalp. I cried. She was put on oral steroids for two days due to a severe chest infection/high IgE (allergy-related antibodies); we took her out of the bath (first time in months two adults didn't have to compete with her scratching frenzies!) and laid her on a towel in amazement - this was what a 'normal' baby was like!
BUT you will work something out to help DD. Have hope.