I hate to admit it, but I've raided the aisles of Walmart, CVS and Walgreens. I take of advantage of sale items as they become available, a whole rack is dedicated to personal hygiene stuff. Fragrance versus Non-fragrance soaps, shampoos. I have stocked up even with Head/Shoulders and other medicated dandruff shampoos. Not to mention, I have several cases of Nix and Rid, in case we have a nit lice problem. Gone are the days that we can delouse with DDT, so I've got some other more body friendly insecticides in case of a louse born infestation.
If preppers have not considered this issue, I'd make every effort to store some in your preps.