making simple calculations from a long list with repeating values

Hello.

I have 4 lists of illness conditions, each with a number next to them which represents the number of days lost to sickness in that year.

I.e.,
Back injury -234
Head injury - 111

etc etc

The problem is not all the conditions are on each list so I cant just copy and paste the lists next to each other.

I have put all the conditions into one list and sorted them alphabetically so I can now see which conditions appear more than once.

Is there a way to add up the totals of days lost due to each condition (possible of 4 values for each condition), without having to do it manually?

hope this makes sense??

many thanks