Is trichodynia a symptom from thinning hair caused by seborrheic dermatitis?

No, this isn't usually a symptom of seborrheic dermatitis. I suggest seeing a hair loss expert now to evaluate and go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

Seborrheic dermatitis does not cause hair loss and hair thinning it self .If you have pain on scalp you would better to have a full exam with an hair expert, surgeon, internalist and/or endocrinologist to find out the reason for that.

Seborrheic dermatitis can cause a range of symptoms including itching, burning and scalp soreness. Trichodynia is typically used to describe scalp pain and soreness in the absence of an obvious inflammatory trigger. So generally, I don't use the term trichodynia in its strictest sense when discussing inflammatory scalp dermatoses like seborrheic dermatitis. But certainly, seborrheic dermatitis can cause scalp symptoms.