Just like many other tasks, editing is possible while you have a head cold. BUT if you are so congested you can’t recall where the ‘h’ goes in ‘that’, it’s probably better to wait until you’re well before you edit.
If you do have to edit, regardless of where the ‘h’ goes, be sure to schedule time to reedit that area when you’re healthy. It’s shocking how congestion clogs up the ol’ brain and there’s a lot that gets missed while editing under the influence of mucus.
Now writing while sick, on the other hand, that can be more… entertaining.
Any writing done while sick will need close revision especially for grammatical and spelling issues (for some bizarre reason, mucus in the head affects the dance fingers do on a keyboard –the thumbs in particular struggle to keep time on that dang space bar).
The need for revision aside, writing with a head cold can prove to be both ponderous and liberating. Words often spill forth as if they are eager to get away from the congestion. But while they may wax poetic, the words do not always carry a lot of forward moment. By that I mean, the words themselves become so engaging and the effort to get them on the page so intense, that the plot, characters, action, all but disappear.
So, if you have to get something done while sick with a head cold, writing may be the better bet.
If at all possible though – take a sick day, or two.
May all your writing and editing days be healthy ones.