Project Zomboid Build 42 First Aid Guide: Wounds & Infection

In Project Zomboid, a scratch you ignore on day one can kill you just as dead as a zombie horde on day seven. Build 42 treats first aid as a real medical loop with a specific order, specific tools, and two completely different types of infection that most players mix up at the worst possible time. Get the loop right and almost every wound in the game is survivable. Get it wrong and a dirty bandage finishes what the zombies started. This guide covers every wound type, the correct treatment sequence, and the fastest way to level the First Aid skill on version 42.20.

What is the correct treatment order?

The sequence matters more than the supplies. Apply steps out of order and you are wasting items or actively making the wound worse.

Remove foreign objects first. Glass shards and bullets block healing entirely. Pull them out with tweezers (glass) or a suture needle (bullets) before touching anything else.
Disinfect the wound. Apply disinfectant, alcohol wipes, or antiseptic directly to the wound before any bandage goes on. Skipping this step is the single most common reason players develop wound infections.
Bandage it. A sterilized bandage is better than a plain one; both beat improvised ripped sheets. The Health Panel tracks each wound individually and shows you exactly what needs attention.
Change dirty bandages on schedule. Bandages progress from clean to dirty to bloody. A dirty bandage sitting on a wound causes infection. Check the Health Panel regularly and swap them out before they reach the bloody stage.
Stitch deep wounds. Standard bandaging is not enough for deep wounds. Use a needle and thread to close them, then bandage on top.

tip

The Health Panel auto-applies first-aid items when your First Aid skill is high enough. Keep the right supplies in your inventory and let the skill work for you.

Health Panel wound tracker

Wound types and how to treat each one

Build 42 has seven distinct wound categories. Each one comes from a different source and needs a slightly different response.

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Fractures deserve extra attention. A splint requires two planks and ripped sheets to craft, and once applied your character needs rest and cannot run. Recovery takes weeks of in-game time, so avoiding the fall or crash in the first place is always the better option.

Splint crafting recipe

Wound infection vs the Knox virus: what is the difference?

This is the confusion that ends more runs than any other mistake. There are two separate infection systems and they require completely different responses.

Wound infection is a bacterial problem caused by dirty bandages or wounds that were not disinfected before bandaging. It slows healing, raises pain levels, and can kill if left completely untreated. The good news: it is fully treatable. Clean the wound, replace bandages consistently, use sterilized bandages going forward, and the infection clears.

The Knox infection (the zombie virus) is a different matter. A zombie bite transmits it with 100% certainty. A scratch or laceration carries a smaller but real chance. Once the Knox infection takes hold, nothing in the game cures it. The first sign is the Queasy moodle appearing a few hours after exposure, followed by fever. Antibiotics, vitamins, and first aid can ease symptoms but cannot stop the outcome.

The practical test: if the Health Panel shows a wound infection but your character is not queasy, you are dealing with bacteria. Treatable. If you just took a bite and the Queasy moodle appears, that character's story is ending. Painkillers and sleep make the final hours more comfortable, but that is the extent of your options.

warning

Never assume a bite wound is just a wound infection because you bandaged it quickly. The Knox virus does not care how clean your bandage is.

What first-aid items should you prioritize?

First-aid kits in Build 42 come in three tiers: ordinary, camping, and military. The military first-aid kit holds the full surgical set and is the one worth keeping in your base. Everything else is a stopgap.

Here is what each item actually does:

Bandages and sterilized bandages cover wounds and slow infection; sterilized versions reduce infection risk more effectively
Disinfectant, alcohol wipes, antiseptic clean wounds before bandaging; all three do the same job
Needle and thread stitch deep wounds shut
Tweezers remove glass shards
Suture needle removes bullets and can also stitch wounds
Splint (crafted) immobilizes fractures; two planks plus ripped sheets
Painkillers and sleeping pills manage pain and fever, including during the Knox endgame
Antibiotics and vitamins help manage wound infection symptoms

important

Always remove glass shards and bullets before bandaging. Leaving foreign objects in a wound stops it from healing entirely, regardless of how many bandages you apply.

How do you level the First Aid skill fast?

Higher First Aid means lower infection chances, faster recovery times, and the Health Panel auto-applying items for you. On 42.20, these are the methods that actually move the XP bar.

Bandage and rebandage repeatedly. Every time you apply or remove a dressing, you earn XP. In a safe location, split a bandage stack and reapply them in sequence. It is repetitive but it works.
Use proper supplies, not improvised cloth. Sterilized bandages and actual disinfectant award more XP per action than torn shirts.
Treat other players in multiplayer. Each patient you treat gives a significant XP bump. If you are playing co-op, position yourself as the group medic early. Check the Project Zomboid multiplayer guide for server setup tips.
Start with the right character build. The Nurse occupation gives +3 First Aid at character creation, which is the fastest possible starting point for this skill.

First Aid pairs well with other survival skills. If you are also working on base construction, the carpentry leveling guide covers the fastest XP routes for that skill using similarly efficient repetition methods.

tip

Treating wounds with sterilized bandages instead of improvised cloth gives more XP per treatment and reduces infection risk at the same time. It is the most efficient use of medical supplies.

Build 42 changes worth knowing

Build 42 brought a significant survival rework. If you played Build 41 and are returning, a few things changed in the medical systems. First-aid kits now have tiered capacity, the Health Panel shows more granular wound data, and the skill leveling rates were adjusted as part of the broader skills overhaul. Your Build 41 saves do not carry over, so every run starts fresh under the new rules. For a full breakdown of everything else that changed, the Build 42 complete changes guide covers the stable release in detail.

The core medical loop itself, clean the wound, bandage it, change dirty bandages, has not changed. What changed is how much the skill level affects outcomes and how the kit tiers distribute supplies. The military kit is now the clear best option for anyone planning extended runs.

For more survival systems, character builds, and base guides, the full Project Zomboid guide collection covers everything from your first week to Louisville endgame runs.

What is the correct treatment order?

The sequence matters more than the supplies. Apply steps out of order and you are wasting items or actively making the wound worse.

Remove foreign objects first. Glass shards and bullets block healing entirely. Pull them out with tweezers (glass) or a suture needle (bullets) before touching anything else.
Disinfect the wound. Apply disinfectant, alcohol wipes, or antiseptic directly to the wound before any bandage goes on. Skipping this step is the single most common reason players develop wound infections.
Bandage it. A sterilized bandage is better than a plain one; both beat improvised ripped sheets. The Health Panel tracks each wound individually and shows you exactly what needs attention.
Change dirty bandages on schedule. Bandages progress from clean to dirty to bloody. A dirty bandage sitting on a wound causes infection. Check the Health Panel regularly and swap them out before they reach the bloody stage.
Stitch deep wounds. Standard bandaging is not enough for deep wounds. Use a needle and thread to close them, then bandage on top.

tip

The Health Panel auto-applies first-aid items when your First Aid skill is high enough. Keep the right supplies in your inventory and let the skill work for you.

Health Panel wound tracker

Wound types and how to treat each one

Build 42 has seven distinct wound categories. Each one comes from a different source and needs a slightly different response.

Loading table...

Splint crafting recipe

Wound infection vs the Knox virus: what is the difference?

This is the confusion that ends more runs than any other mistake. There are two separate infection systems and they require completely different responses.

warning

Never assume a bite wound is just a wound infection because you bandaged it quickly. The Knox virus does not care how clean your bandage is.

What first-aid items should you prioritize?

Here is what each item actually does:

Bandages and sterilized bandages cover wounds and slow infection; sterilized versions reduce infection risk more effectively
Disinfectant, alcohol wipes, antiseptic clean wounds before bandaging; all three do the same job
Needle and thread stitch deep wounds shut
Tweezers remove glass shards
Suture needle removes bullets and can also stitch wounds
Splint (crafted) immobilizes fractures; two planks plus ripped sheets
Painkillers and sleeping pills manage pain and fever, including during the Knox endgame
Antibiotics and vitamins help manage wound infection symptoms

important

Always remove glass shards and bullets before bandaging. Leaving foreign objects in a wound stops it from healing entirely, regardless of how many bandages you apply.

How do you level the First Aid skill fast?

Higher First Aid means lower infection chances, faster recovery times, and the Health Panel auto-applying items for you. On 42.20, these are the methods that actually move the XP bar.

Bandage and rebandage repeatedly. Every time you apply or remove a dressing, you earn XP. In a safe location, split a bandage stack and reapply them in sequence. It is repetitive but it works.
Use proper supplies, not improvised cloth. Sterilized bandages and actual disinfectant award more XP per action than torn shirts.
Treat other players in multiplayer. Each patient you treat gives a significant XP bump. If you are playing co-op, position yourself as the group medic early. Check the Project Zomboid multiplayer guide for server setup tips.
Start with the right character build. The Nurse occupation gives +3 First Aid at character creation, which is the fastest possible starting point for this skill.

tip

Treating wounds with sterilized bandages instead of improvised cloth gives more XP per treatment and reduces infection risk at the same time. It is the most efficient use of medical supplies.

Build 42 changes worth knowing

For more survival systems, character builds, and base guides, the full Project Zomboid guide collection covers everything from your first week to Louisville endgame runs.