Looking through Edward's service record, you will find a page for his discharge from the 4th (?) London General Hospital RAMC (Royal Army Medical Corps) on the 23 June 1916. His disease is shown as 'SW Finger' -- your initial post asked for clarification of 'Whittons' -- this entry (as suggested by JenB) is actually 'Whitlow' -- a painful finger condition caused by infection. I have attached images of the relevant page of his service record (courtesy of Find My Past) and also an explanation of 'whitlow'.