Msg 8905: DBCC CHECKALLOC Error Messages
I would suggest to take a backup and restore the database to a different server and then run DBCC CHECKDB ...repair_allow_data_loss. This way you will know if there is any data loss or not.

Refer to my answer for more details.

If you have a good backup that you can restore, I would prefer to go with that and export the data out of the corrup database. You can use redgate's data compare (not free, but I have used it and its a lifesaver).

Make sure you do diagnosis of your hardware and update driver firmware to latest version and are on the latest supported service pack for sql server 2008R2.