The US Military considers hay fever a “respritory problem” and therefore sufferers are rejected for pilot training.
Because of this I didn’t join the marine corps, which in retrospect turned out well for me.
Please excuse my ignorance here - I’m not much up on medical terminology, so I’m sure I’ll make a few mistakes.
My niece had toxic shock syndrome when she was 14 years old. She was in intensive care, and things were looking very, very bad. I believe the term is that she went septic - basically she was dying. It’s my understanding that at the point where she was, thing were going to go one of three ways, none of which were especially easy to deal with.
She surpised us all and went a fourth way. She eventually recovered and all is fine.
Months later, she was diagnosed with a rare blood condition - there’s a name for it, but hell if I know what it is - but basically when she was lying in intensive care and we were waiting for her to die in one of 3 ways, this blood condition caused her to go a fourth way and recover. I believe it had something to do with how her blood clots in very particular situations.
Sorry this was so vague, but it seemed to fit the OP.
There was some reports a while back about Hepatitis A blocking asthma and alergies. In most people Hepatits A is fairly mild and only causes cold-like sysmptoms when you get it. Back before the 1970’s they say virtually everyone either had Hepatitis A or was exposed to it and somehow this could stop carriers from developing asthma and allergies. Since the Western World is now so “germ-phobic” it is estaimated that only 25 to 30 percent of people carry the virus and scientists point to the parallel rise in allergies and asthma. In searching casually on the net I couldn’t find any recent updates or refutations to the original study.
Here are some links to the original study:
BBC
The Nature study (if you want to buy it)
Lycanthropy (the disease, not the curse) is believed to dramatically improve the rate at which flesh wounds will heal. This has proven difficult to verify however because when a lycanthrope is known to have received a flesh wound several other similar wounds typically follow in rapid succession facilitating the ultimate demise of the patient. Nonlethal encounters with lycanthropy sufferers sometimes result in the patient eluding such attacks and returning after a brief hiatus only to display no sign of previous injury. Again, this is primarily hearsay because individuals in a position to witness the initial injury as well as the subsequent healing are frequently eaten by the patient in the second encounter and are thus not reliable witnesses.
For some reason I alwasy found it fascinating that some of the bacteria “infecting” our intestine are a major source of vitamin K, which helps our blood clot.