Does seborrheic dermatitis and vitamin d deficiency cause hairloss?

Hair loss can be associated with a Vitamin D deficiency. 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

Both are known to cause some degree of hair loss.  Depending on whether you have other causes, you should be able to regrow your hair after proper treatment of both of these factors. 

For most people, mild seborrheic dermatitis and vitamin d deficiency do not cause significant hair loss. Seborrheic dermatitis, if moderate or severe might cause a bit of shedding (telogen effluvium) - but it needs to be fairly severe. There has never been definitive proof to date that for hair thinning, that vitamin D supplementation helps. There does seem to be some association but its more complex than simply taking vitamin D pills.