I'm always looking to take things out of my pack and resist buying the latest shining thing to add to the pack.
I've seen folks with giant 3lb first-responder type first aid kits, and too many folks with NO kit at all.
I've settled on a very small dedicated stuff sack to carry my kit.
Bandaids, paper tape, 1 and 2" adhesive pads, mole skin and mole foam, lots of blister stuff. A fair amount of acetaminophen for aches and pains, amount dependent upon the type of trip.
A tiny bottle of betadine.
A small zip lock of wet wipes.
a very small roll of that stretchy tape stuff to wrap an ankle
some KT or leukotape for hot spots when walking for miles in wet shoes.
Replying to my own topic, here's some philosophy (philosophy - get it?)
When hiking/backpacking, everyone should carry their own first aid kit.
Reason being, if I use my stuff on YOU, then I don't have it for ME.
Don't rely on that one guy or gal, who is a nurse or medic or volunteer first responder, who always carries a 5lb hospital grade medical box and is always looking for the opportunity to tape you up.
First, what is your level of first aid training? That has a lot to do with what should be in your kit. Training is a lot more important than stuff. Being able to recognize serious, often subtle conditions is very important - what does it mean if pupils of someone who has just tripped and fallen are different in size?
I would add in, just thinking off hand, a couple of 3"elastic bandages - really versatile items and perhaps a few 4" sterile dressings.
It is worthwhile to look over the rest of your kit in search of items that will be useful in first aid. How would you fashion a splint for a broken/badly sprained ankle or leg (you usually can't tell the difference without an x-ray). Could you incorporate a trekking pole (or pieces), tent poles?. What about padding for the splint? Out of tape? How about the duct tape in your repair kit? and so on.... Good improvisation can be just as effective as specialized, one use items, if done right.
If you are deep in the woods, how will the victim reach definitive care? Is the person alert, oriented, and generally OK? Is the person properly hydrated? (most of us are typically slightly dehydrated). Can you keep the victim warm or cool as conditions require?
If you are dealing with a serious situation, your most important item may be a cell/PLB to summon outside assistance. Signalling gear (whistle and signal mirror) come into play here, or possibly a good, roaring signal fire....
Again, so much comes down to training and experience,using thoughtful judgment.
My comments are based on training to nationally certified EMT level and extensive experience at back country SAR scenes. I would loe to hear from higher level medical professionals on this subject.
Be careful with acetaminophen (aka Tylenol) Overdoes can cause liver damage. It is good at reducing fevers but no so great for "aches and pains" caused by inflammation. It would not be my first choice of pain relief drug take backpacking.
Unless you have conditions that prevents you using it, ibuprofen (aka advil) is a better over the counter drug for inflammation and pain control. I have heard of it referred to jokingly as "vitamin I" by various backpackers. It is also supposed to be helpful for altitude sickness.
What to carry depends on the length of the trip. The most common "injuries" and "conditions" are dehydration, small cuts and scrapes, dry and cracking skin, problems with finger and toe nails, blisters, insect bites and associated allergic reactions, allergic reactions to certain plants, sun and wind burn, bowel issues, and chafe in the nether regions.
I'm not a First Aid guru but this is my working list. It is only an example and it may not be adequate for you so make your own informed choices. You should also carry a suitable supply of any prescription medications you need and if you are allergic to bee stings, appropriate measure to counteract that. Women may require additional items for longer trips.
Short hike...Focus on dehydration, sun/wind burn and small cuts and scrapes
Day hike or Overnight add...Focus on pain relief, allergic reactions, and foot care since you need to get home
Overnight or Multi-night add...Focus on bowel and chafing problems.
If you are that badly injured you are going to need help and evacuation anyway
More remote and lonely trips will require more knowledge and supplies.
The trick is getting the quantities right. You are unlikely to need the various supplies and unctions in the quantity/volume they are typically sold in so you probably want to re-package things. This should not take up much space or weigh much.
oh and I forgot splinters...
so to Day hike and Overnight add..
I might add some decongestant tables like psuedophedrine to the longer trip drug list since they can be helpful controlling certain symptoms. If you suffer from "hay fever" or similar allergies you should know what works for you and take that along on hikes and longer trips.
One other thought. Clean water is also an essential first aid tool. For long day-hikes overnights and longer having some kind of water filter along is a good idea. Hiking filters like the Sawyer Squeeze with get rid of spores and bacteria which should reduce the chance of adding infection but for long trips I also carry Aqua Mira as a backup. It also kills viruses and so can be used as an addition for any particular gnarly water sources that are, say, near livestock. The main concern in the US is hantavirus spread by rodents. I would be inclined to add Aqua Mira to water used for cleaning any wounds that were more that a surface scratches. Aqua Mira takes 15 mins to work and staunching blood flow is more important on deep wounds so this is more for secondary cleaning.
an water is a very worthwhile commodity; it can be obtained also by boiling water briefly, cooling it and then irrigating the cut, although usually that step is not necessary. Boiling will kill everything and is more dependable method than filtering or any chemical additives.
Old Guyot mentions hanta virus as the major concern in the US. I beg to differ. HV is not present over many portions of the country. It is usually contracted by intimate contact with rodent feces, nesting material, etc. Contagion is actually rather rare.
I guess I was thinking of the Southwest states and particularly the southern end of the CDT where water source are few and far between and often shared with livestock. So picking out hanta "in the US" was a overstatement. But, anywhere there are cattle there are rodents and it is not uncommon to find a dead rodent in an open water tank. If that is the water source you have to use ...
The general consensus is that water born viruses are relatively rare in the US and that is why you can generally get by with a filter like the Sawyer Squeeze that is not effective for them.
Boiling water for first aid is an option but it assumes you are carrying a pot, stove, fuel and lighter, you are calm enough to set that up and can wait for it to heat up, boil for 1 to 3 minutes depending on altitude, then cool down enough to use. I don't usually carry a stove on a day hike and might not on an overnight or even a longer trip when even canister stoves a banned due to fire danger. Also boiling water for 1 to 3 minutes takes quite a lot of fuel.
Filters are the best primary option in my view because they are quick, don't use fuel and remove particulates and small creatures making sketchy water palatable as well as safe.
But my point was more that carrying Aquamira in your first aid kit is a good idea. It has a long shelf life, is easy to use, works fairly quickly and it only need add 2oz or less to your base weight. While you could argue it is a "packing your fears" item if you are already carrying a filter, having a convenient backup to a relatively fragile, easily lost or even forgotten water filter and a way to cope with some hopefully unusual circumstances seems worth the extra weight to me.