What is a good shampoo for hair loss?

As a adjunct to proper treatment of androgenetic alopecia, the use of an OTC ketoconazole shampoo might be of some limited value by suppressing the yeast organisms that typically inhabit all scalps that might be contributing to subclinical inflammation, which may be an aggravating--but not causative-- factor. But, by itself, the use of any shampoo will not really treat alopecia, and its use might delay proper medical treatment; such delays can translate into worse treatment outcomes. As dermatologists specialize in the treatment of hair, skin and nail disorders, you would be wise to consult a board certified dermatologist asap. The earlier proper treatment is initiated, the more likely there will be a successful outcome. Proper treatment can include the use of a variety of prescription strength topical treatments (over and above the simple use of topical Rogaine--which by itself is seldom particularly successful) and oral medications (other than Propecia, which may result in unwanted sexual side effects, such as loss of libido or ED). So to repeat, you would be wise to consult an experienced dermatologist and not waste time with OTC shampoos, oral supplements, like biotin, or the anecdotal advice found on Dr. Google or Dr. Instagram. Hope this helps and best of luck.