The 1st thing I do with a new eclipse workspace is set preference 'enable spell checking' to false.
By default, the eclipse spell checker red underlines words in your files that it doesn't recognise.
IMHO, the default should be false.
Ian, sorry that the default for this function is not ideal for you. The default will never satisfy all users of course but you can always export a set of workspace preferences, in an epf file, and import that file each time you create a new workspace, as mentioned in the chosen answer to this StackOverflow question: https://stackoverflow.com/questions/6295066/turn-off-spell-checking-in-eclipse-for-good
I'm not sure what your particular work situation is but if you have a number of colleagues with the same issue you may want to take a look at our SDC project which can provide this functionality. You can read more about SDC here: https://www.genuitec.com/products/sdc/