A first aid kit or medical kit is a collection of supplies and equipment used to give immediate medical treatment, primarily to treat injuries and other mild or moderate medical conditions. There is a wide variation in the contents of first aid kits based on the knowledge and experience of those putting it together, the differing first aid requirements of the area where it may be used, and variations in legislation or regulation in a given area.

The international standard for first aid kits is that they should be identified with the ISO graphical symbol for first aid (from ISO 7010), which is an equal white cross on a green background.

Standard kits often come in durable plastic boxes, fabric pouches or in wall mounted cabinets. The type of container will vary depending on the purpose, and they range in size from wallet-sized through to a large box. It is recommended that all kits are kept in a clean dust- and damp-proof container to keep the contents safe and aseptic.

Contents of first aid kits

Commercially available first aid kits available via normal retail routes have traditionally been intended for treatment of minor injuries only. Typical contents include adhesive bandages, regular strength pain medication, gauze and low grade disinfectant.

Specialized first aid kits are available for various regions, vehicles or activities, which may focus on specific risks or concerns related to the activity. For example, first aid kits sold through marine supply stores for use in watercraft may contain seasickness remedies.

Common items

Common kits may contain:

• Thermometer
• Adhesive dressings
• Antiseptic solution (most commonly povidone iodine or hydrogen peroxide)
• Bandages
• Cotton balls or swabs
• Emergency blanket
• Gauze sponge
• Gloves
• Hand sanitizer
• Ice pack
• Saline solution
• Tweezers

Trauma injuries

Trauma injuries, such as bleeding, bone fractures or burns, are usually the main focus of most first aid kits, with items such as bandages and dressings being found in the vast majority of all kits.

• Adhesive bandages (band-aids, sticking plasters) - can include ones shaped for particular body parts. 
• Dressings (sterile, applied directly to the wound)
• Bandages (for securing dressings, not necessarily sterile)          

         Gauze roller bandages – absorbent, breathable, and often elastic

         Elastic bandages – used for sprains, and pressure bandages

         Adhesive, elastic roller bandages (commonly called 'Vet wrap') – very effective pressure bandages and durable, waterproof bandaging

        Triangular bandages – used as slings, tourniquets, to tie splints, and many other uses

• Butterfly closure strips – used like stitches to close wounds, usually only included for higher level response as can seal in infection in uncleaned wounds.
• Saline – used for cleaning wounds or washing out foreign bodies from eyes
• Soap – used with water to clean superficial wounds once bleeding is stopped
• Antiseptic wipes or sprays for reducing the risk of infection in abrasions or around wounds. Dirty wounds must be cleaned for antiseptics to be effective.
• Burn dressing, which is usually a sterile pad soaked in a cooling gel
• Adhesive tape, hypoallergenic
• Hemostatic agents may be included in first aid kits, especially military, combat or tactical kits, to promote clotting for severe bleeding.

Personal protective equipment

The use of protective equipment or PPE will vary by the kit, depending on its use and anticipated risk of infection. The adjuncts to artificial respiration are covered above, but other common infection control PPE includes:

• Gloves which are single-use and disposable to prevent cross infection
• Goggles or other eye protection
• Surgical mask or N95 mask to reduce the possibility of airborne infection transmission (sometimes placed on patient instead of caregivers. For this purpose the mask should not have an exhale valve)
• Apron

Insturements and equipment 

• Trauma shears for cutting clothing and general use
• Scissors are less useful but often included (usually to cut medical equipment off or smaller)
• Tweezers, for removing splinters, amongst others.
• Lighter for sanitizing tweezers or pliers etc.
• Alcohol pads for sanitizing equipment, or unbroken skin. This is sometimes used to debride wounds, however some training authorities advise against this as it may kill cells which bacteria can then feed on
• Irrigation syringe – with catheter tip for cleaning wounds with sterile water, saline solution, or a weak iodine solution. The stream of liquid flushes out particles of dirt and debris.
• Torch (also known as a flashlight)
• Instant-acting chemical cold packs
• Alcohol rub (hand sanitizer) or antiseptic hand wipes
• Thermometer
• Space blanket (lightweight plastic foil blanket, also known as "emergency blanket")
• Penlight
• Cotton swab
• Cotton wool, for applying antiseptic lotions.
• Safety pins, for pinning bandages.

Medication

Medication can be a controversial addition to a first aid kit, especially if it is for use on members of the public. It is, however, common for personal or family first aid kits to contain certain medications. Dependent on scope of practice, the main types of medicine are life saving medications, which may be commonly found in first aid kits used by paid or assigned first aiders for members of the public or employees, painkillers, which are often found in personal kits, but may also be found in public provision and lastly symptomatic relief medicines, which are generally only found in personal kits.

Life saving

Aspirin primarily used for central medical chest pain as an anti-platelet

Epinephrine autoinjector (brand name Epipen) – often included in kits for wilderness use and in places such as summer camps, to temporarily reduce airway swelling in the event of anaphylactic shock. Note that epinephrine does not treat the anaphylactic shock itself; it only opens the airway to prevent suffocation and allow time for other treatments to be used or help to arrive. The effects of epinephrine (adrenaline) are short-lived, and swelling of the throat may return, requiring the use of additional epipens until other drugs can take effect, or more advanced airway methods (such as intubation) can be established.

Diphenhydramine (brand name Benadryl) – Used to treat or prevent anaphylactic shock. Best administered as soon as symptoms appear when impending anaphylactic shock is suspected. Once the airway is restricted, oral drugs can no longer be administered until the airway is clear again, such as after the administration of an epipen. A common recommendation for adults is to take two 25mg pills. Non-solid forms of the drug, such as liquid or dissolving strips, may be absorbed more rapidly than tablets or capsules, and therefore more effective in an emergency.

Pain killers

• Paracetamol (also known as acetaminophen) is one of the most common pain-killing medications, as either tablet or syrup.
• Anti-inflammatory painkillers such as ibuprofen, naproxen or other NSAIDs can be used as part of treating pain from injuries such as sprains, strains and bone fractures.
• Codeine is both a painkiller and anti-diarrheal.

Symptomatic relief

• Anti diarrhea medication such as loperamide – especially important in remote or third world locations where dehydration caused by diarrhea is a leading killer of children
• Oral rehydration salts
• Antihistamine, such as diphenhydramine
• Poison treatments
• Smelling salts (ammonium carbonate)

Improvised uses

Besides the regular uses for first aid kits, they can be helpful in wilderness or survival situations. First aid kits can make up a part of a survival kit or a mini survival kit in addition to other tools.