Is this safe to take in a daily one time dose of 25 or 50mg to help with insomnia on it's own with no other medication?

Of all the pharmaceutical sleep aids out there diphenhydramine (Benadryl) is actually the one I would consider the safest.

I'm reading about really awful withdrawal symptoms on various websites and forums though most seem to be taking triple digit doses in mg. I don't intend to go over 50mg daily if I do decide to take it. If I get diminishing results on this dose, I'll just taper off it and then stop completely.

I've also just started looking into sleep aids based on "doxylamine succinate". Any advice on whether to take Diphenhydramine HCI or Doxylamine Succinate would be appreciated.

Diphenhydramine is stronger and longer lasting than doxylamine (Unisom), although diphenhydramine can also leave you drowsy in the morning.  Both have been reported to give some individuals a "hangover".

There are safer ways to induce sleep such as taking a calcium/magnesium before bed or glycine, sedative herbs, etc.  Or address the cause of the insomnia such as hypothyroidism, overuse of caffeine, etc.