Scalps are the hardest place to treat for lots of folks. But over the years we've found ways to treat this that help almost EVERYBODY!!
Ways to treat
Slow way -- Traditionally, application of steroid lotions (actually, solutions are best) at nighttime. This will work, but the penetration of the medicine is poor due to the build-up of scale. So you may get some improvement this way, but it's preciously slow.
Much Faster way -- apply about thirty drops of a cortisone solution to the scalp at nighttime. My favorite is Lidex (fluocinonide), but many will work, some slightly stronger, some not. No need to rub this in. It diffuses over an area and eventually all the drops overlap. Now apply a plastic shower cap. This is NOT a terry cap or terry lined. It is a simple plastic shower cap. Pull it over your ears to make it easier to tape on. Tape down (with paper tape so you don't cause irritation) all available edges so that it's securely on, and relatively airtight. Sleep with this on all night. Remove in the morning, and you will look like the wreck of the Hesperus. Shampoo with a nice tar shampoo (the best is Pentrax) -- later twice each time, leave the second lathering on for five to seven minutes while you wash the rest of you in the shower. You may blow dry, but do not scratch or attempt to remove attached scale. That scratching and trauma is what makes the psoriasis so much worse.
Use Kenalog Spray (comes in 63g spray can in USA) twice during the day. You don't need much of this. Just a slight little spray, so you don't waste the medicine. No need to WET the scalp with Kenalog.
If you have severely adherent scale, Baker's P&S is the scale remover you need. You must apply this to wet the scalp every other night and just leave it on, shampooing in the a.m. as we discussed above. Use it every other night, alternating with the Lidex under plastic occlusion.
All this is very important to do in exactly the manner suggested. In several days, most patients are remarkably better.
There are many other ways, so let's talk if you do this and no help is forthcoming. Print this out and take it to your doctor. The best dermatologists are willing to listen to any therapy for consideration. It is the patient who is most important.
These are not new techniques for treating psoriasis. It's just that many don't use them any more, and they work beautifully.