Delimited data sets in Excel

Hello,

I currently extract data from our grants system into an Excel spreadsheet which shows all the subjects a reviewer has selected. It extracts all the information into one cell per person, so that it looks something like this:

subject a, subject b, subject c

I'd like to create a pivot table of subjects to identify gaps, but haven't been able to work out an efficient way of doing this. I've tried using the text to columns function using the commas as the delimited but the problem I have is that some subjects have commas within them. For example, Chemistry, applied is one subject but choosing the text to columns option means that chemistry and applied end up in two different cells.

Thank you for your help!