Altitude illness comes in three forms: AMS, HACE, and HAPE. How to recognise each one, why sleeping altitude is the number that matters, and why descent is the only real treatment.

Cold injury explained: how to tell frostnip, frostbite, and trench foot apart, how to rewarm each safely in the field, and the refreezing mistake that costs fingers and toes.

Hypothermia can strike on any wet, windy day, not just in deep cold. How to recognize it at every stage and safely rewarm someone in the field, from mild shivering to a severe emergency.

The rash-and-burn plants every hiker should recognize. How to identify poison ivy, oak, and sumac, avoid the urushiol that causes the rash, decontaminate fast, and treat it — plus giant hogweed, whose sunlight-activated sap burns anyone it touches and can harm your eyes.

In the backcountry the danger isn’t usually the wound; it’s the infection that follows. How to clean, close, and dress a wound in the field, spot infection early, and know when it’s time to head out.

Heat illness is a ladder you can step off early. Recognizing and treating heat cramps, heat exhaustion and heat stroke, plus hyponatremia, which looks identical and needs the opposite treatment.

A limb injury far from the trailhead can strand you. How to assess the injury, improvise a splint and sling, protect circulation, and decide when to walk out or call for help.

Help can be hours away, so the first minutes are yours. The order that saves lives: scene, bleeding, airway, breathing, warmth, then the evacuation decision.