working out when you are sick

I am going to touch wood and say that thankfully I haven't been sick for ages! That's probably a jinx right there.  But what happens when you get sick and you still want to work out, what are the rules - are we allowed?
Common sense screams out that we should fully recover before doing a strenuous intense workout, but would it be ok to just show up and go through the motions with a lighter load? Here is how I would approach it;


I WOULDN'T WORKOUT IF:

• I had a fever
• was highly contagious
• if I  had the trots or nausea

BUT I WOULD TRY TO WORKOUT IF:

• I had a mild cold and the worst was over. For example a runny nose, scratchy throat, sneezing - but I would keep the workout low-intensity.

The worst thing to do is to do a crazy high-intensity workout and hamper your recovery.

Another theory I have heard before is 'if it [the illness] is above the neck, it’s okay, but if it’s below the neck, it’s not okay'.

How do you deal with sickness and exercise?