Hi underneath32, have you looked at the dermnet.com website, which has many photos of various people with seb derm: http://hardinmd.lib....dermatitis.html
You said you were leaning to seb derm, which is usually caused by malassezia yeasts (aka fungus). Flat red bumps and plugged pores are a sign of a malassezia-induced skin condition, but you will need to make up your own mind. Nizoral 1% is OTC in the US but it is sold only on the web, for example, walgreens.com.
You could do a differential diagnosis by using effective anti-fungal treatments. As for your choice of shampoos, climbazole is a more effective anti-fungal than ketoconazole, (the active ingredient in Nizoral 1% shampoo). Here’s a list of all the OTC climbazole shampoos:
1) Hegor’s 150 (1.5% Climbazole), which is made in France and is available in the US only on eBay and will be shipped from Bulgaria.
2) Alderma’s Bioderma Sensibio DS Gel containing unstated amounts of climbazole and piroctone olamine, which is available on Amazon and ships from Portugal.
3) Eucerin’s DermoCapillaire Antidandruff Gel Shampoo containing 0.5% piroctone olamine and 0.45% climbazole, which is sold only in the EU and is not available online, as far as I can tell.
I think many people get good results using only a shampoo, but I didn’t. I started out using Nizoral 2% ketoconazole cream, which is not OTC in the US but can be mail ordered from India. The only OTC anti-fungal in the US is Lotrimin Ultra, which is 1.0% Butenafine Hydrochloride, and it’s on the shelf of every US drug store. There's a $2-off coupon at the manufacturer's website. The Lotrimin AF is not very effective so be sure you try the Ultra, if you decide to try a lotion.
I tried Aloe Vera and found that it helped a little, but I recently started adding 2% to 5% Xylitol to everything I use. I’m inferring from candida biofilm research, that Xylitol prevents biofilm formation by making the keratin too slippery for the fungus to interact with the skin. We will always have malassezia because it’s commensal, or normally found, on all mammals’ skin. Malassezia creates a biofilm that is mostly your own keratin, in which it evades detection by the immune system. The flat bumps are the biofilm. Once you start treating, you'll find a lot of biofilms that were previously invisible.
The healing process in treating a fungal skin condition is like a time machine slowly going backwards. The medicine slowly dissolves the cells walls of the yeast and the contents of the yeast cells leak out and it dies. The redness results from your body’s immune system recognizing that there are fungal foreigners, to which the body’s first healing reaction will be redness and inflammation, which is normal. Do not be dismayed by additional patches of skin redness – your body is healing, although it may take weeks or months to become normal.
My first or second post at this forum has more information on OTC malassezia treatments.