Solved Adding IPTC and Comment when a jpeg has none.

[Timevoyager]

In doing online research for writing or gathering photographic ideas, I like to make sure I credit the source of the photo. I noticed there is often no IPTC or Comment file and no way to add information using Irfanview. I solved this by simply using a program called GIMP, a GNU image manipulation program, downloaded from the web. In GIMP's menu, I opened "Properties" and found the place to enter a basic text comment. I then reopened the jpeg image in Irfanview and found the IPTC and Comment buttons were added! Simple!

[Bhikkhu Pesala]

You don't need to use GIMP for this. You can add IPTC data to any JPG from the Image Information dialogue in IrfanView, then click on Write to save it.