My first aid kit is my entire gear list.

Pack stay, blue foam sit pad or trekking pole = splint for a limb
Trekking poles + jackets = travois/stretcher
hydration bladder under pressure = irrigation for wounds
extra clothing/sleeping quilt = warming gear for hypothermia vic
bandanna - tourniquet/bandage cover/washcloth

Then the kit itself:
bandaids, several sizes
butterfly closures
ace wrapper
medical tape (around one of the pill bottles)
Leukotape (around the DEET sprayer, replaces moleskin for preventing blisters)
sterile gauze pads
gauze wrap
a tick puller (better for folks with shaky hands than tweezers, has a magnifying glass too)
alcohol wipes (to sterilize knife edges, etc. not for wounds)
nonlatex gloves (many uses, including a breath mask for CPR if you cut off a finger)
packet vinegar (nettles leave stingers behind, vinegar melts them away)
tiny dropper bottle of sting eze
packets of neosporin
ibuprofen 200 mg pills
extra strength excedrin migraine - because if a migraine begins it's best to catch it before the prescription is necessary
one prescription pill for migraine (melts on tongue, my usual symptoms are sound sensitivity, debilitating brain-melting pain and projectile vomiting of anything ingested once the migraine is in full force)
sudafed (the real kind, not the neutered junk, because allergies are heck)
zyrtec (takes care of the allergies to a point)
benadryl (general allergy reaction treatment, also a sleep aid)
immodium (because diarrhea is dangerous in the wilderness)
hydropel - for long days - does a great job of reducing hot spots

Leatherman Micra - has a scissors for clipping nails, cutting tape/gauze, also tweezers and a bottle opener and a sharp but short knife blade

Other emergency gear to maintain good health would include a supply of Micropur tabs, in the event the filter breaks, electrolyte tabs (which I don't use under normal circumstances), fire making tools (storm proof matches, the extra bic riding around in the bandaid pouch, ball of dryer lint)...
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki