Would it be possible to take a photograph of this rash on the shoulder at your convenience?
There are two possibilities given your history. The first is Scalp Psoriasis and the second is Seborrheic Dermatitis (Seb Derm). Both of these can affect the scalp as well as body skin and will explain both your scalp and shoulder symptoms.Psoriasis is an autoimmune condition affecting the scalp and skin most commonly.Seb Derm is a condition where the body loses tolerance for a yeast called Malassezia (which is present normally on all our skins) and starts attacking it leading to redness and scaling. Itching is variable but can be severe.If possible I would recommend discussing both of these with your doctor since they are best treated with prescription products. If not here is what I would recommend as far as an over the counter regimen goes:Psoriatrax 5% Coal Tar shampoo + Nizoral-AD shampoo: Mix in equal proportion and lather onto the scalp. Leave on for 5 minutes and then rinse off. Do this every alternate day. On the off days use a regular shampoo like Dove.Mg 217 Psoriasis lotion: Apply once at night before sleeping and then wash off in the morning. Use daily for 6 weeks and then 2-3 times a week for 3 months.On the shoulder patch apply 1% Cortizone cream mixed in equal parts with 1% Clotrimazole cream. Apply twice a day for 14 days and then once at night for 4 weeks.Omega-3 Fatty Acid capsules: one morning and evening for 3 monthsTab Claritin 10 mg twice a day for 14-21 daysNo hair oil applicationNOTE: All of the above are available without a prescription on www.amazon.com