I've mentioned this previously: I have alopecia universalis. All my hair fell out about 3 months after I suffered anaphylactic shock - possibly as a result of someone spiking my cocoa with unknown pills (probably a codeine derivative). I don't recall having any form of injection. In my case it affected ALL keratin-producing cells including fingernails (but those grew back).

Worth mentioning that the poison they use for chemo-"therapy" can cause hair loss, too.