Here's an interesting case of vitamin deficiency you should read.
Biotin deficiency is rare. Nice to know for exams though. Soooo.. I made a mnemonic. Biotin reminds me of the comic character, Tin Tin!
Symptoms of deficient biotin intake are:
Rashes, including erythematous periorofacial macular rash
Fine and brittle hair
Hair loss or total alopecia
Mild depression, which may progress to profound lassitude and, eventually, to somnolence
Changes in mental status
Generalized muscular pains (myalgias)
Hyperesthesias and paresthesias
Nausea, occasionally severe
Related post: Biotin mnemonic