Most store-bought first aid kits are built for car camping: bulky, padded, and full of things you'll never use. Most DIY ultralight kits err the other way and can't handle a real blister day. Here's the checklist we'd build from scratch, with honest gram counts and the reasoning for every cut.
Wound care (the non-negotiables)
Assorted bandages (4 g), sterile gauze pads ×2 (6 g), alcohol wipes ×4 (8 g), antibiotic ointment single-use packets ×2 (4 g), and super glue (4 g) — which closes small splits in fingertips and heels better than any bandage. Skip the roll of medical tape; Leukotape does its job and two others.
Blister care
Blister prevention starts while the skin is intact, at the first sign of rubbing or warmth. Skinshield is a rounded 50 × 70 mm rayon patch with zinc oxide adhesive; a packet of 20 weighs 17 g. The full patch is sized to cover the back of a hiker's heel. For a smaller rub area, leave the backing on, trim with small scissors, and round any new corners. Apply before a blister forms. If a blister has already formed or been drained, use an appropriate blister dressing instead. A full roll of Leukotape is over 100 g — carry a yard of it on a spool (14 g) instead. Add a needle (shared with your repair kit) for draining. The technique matters more than the supplies: see First Aid for Feet and Leukotape vs Moleskin.
Medications (tiny weight, big consequences)
Ibuprofen ×8 (3 g), Benadryl ×4 (1 g — allergic reactions in the backcountry are a genuine emergency), anti-diarrheal ×4 (1 g — dehydration from GI illness ends hikes), and any personal prescriptions. Repackage everything into a tiny zip bag with a label; bottles are wasted grams.
Water backup
Purification tablets ×10 (6 g). If your filter freezes or clogs, tablets are the difference between drinking and gambling.
What stays home
Full-size scissors (the small scissors on a compact pocket knife are enough if you plan to trim Skinshield), trauma shears, ace bandages (Leukotape plus a buff improvises), CPR masks, snake bite kits (they don't work), and anything you don't know how to use.
The gear-repair half
A hike ends just as fast from a punctured pad as a rolled ankle. That's why we pair the medical list above with a 14 g repair spool, fabric patches, and pad patches. Our First Aid & Repair Kit is exactly this checklist pre-assembled: everything above plus the full repair system in a weatherproof DCF pouch at 70 g. Build it yourself or buy it built — either way, know every item in it before you need one. For keeping it stocked mid-trail, see Restocking on the Trail.
