Most wounds heal whatever anyone does to them. The small number that go wrong mostly go wrong for two reasons: something was left in them, or something unhelpful was put on them. Both are avoidable in the first five minutes, and both are commonly caused by trying to help.
1. Irrigation, and why tap water is fine
Clean running tap water is a reasonable irrigant for an ordinary fresh wound. For uncomplicated cuts and grazes in a country with potable water, trials comparing it against sterile saline have not found a higher infection rate, and several found a non-significant trend the other way. It is free, it is available immediately, and the volume matters more than the sterility. Moderate
The grade, since this site grades things. The earlier Cochrane versions concluded tap water should be preferred to saline for acute wounds on cost and availability. The current version, updated in September 2022, rates the underlying evidence as low to very low certainty — the trials are small and inconsistently defined. What that means practically: tap water is a sound default and there is no case for delaying irrigation to find saline, but this is a reasonable practice rather than a proven superiority. The trials also excluded the wounds where it matters most — bites, punctures, heavily contaminated wounds, anything with a foreign body, and immunocompromised patients. Those need a clinician, not a tap.
- Use plenty and use flow. A minute or two under a running tap, not a wipe with a damp cloth. For a gritty graze this is the difference between healing clean and tattooing grit permanently under the skin.
- Lukewarm, not hot. Cold water is uncomfortable and makes bleeding harder to see; hot water restarts it.
- Get the grit out. Anything embedded that will not come out with irrigation needs a clinician. Grit left in a graze becomes a permanent blue-grey mark, and that is the commonest lasting consequence of a badly cleaned knee.
- Do not scrub. Scrubbing damages the tissue that is going to heal it and drives contamination deeper.
- Antiseptics are optional and slightly double-edged. Povidone-iodine or chlorhexidine around the wound is reasonable; the older habit of pouring strong antiseptic into a wound harms healing tissue and offers little over irrigation. Never hydrogen peroxide in a wound.
2. Out and about, with nothing
This is the situation most guidance ignores, and where the improvised choices matter most.
| Reasonable | Actively harmful |
|---|---|
| An unopened bottle of drinking water. Pour it, do not dab — the flow is the point | A part-used bottle that has been carried around warm for hours or days. Backwash plus warmth grows a substantial bacterial load. A bottle opened an hour ago and kept cool is a different thing — the problem is time and temperature, not the fact that the seal is broken |
| Direct pressure with the cleanest cloth available, even a T-shirt. Stopping bleeding outranks sterility | A used tissue. It disintegrates into the wound, leaving fibres that have to be picked out later, and it is not clean |
| Air drying, if there is nothing clean to dry with. Slower, and better than the alternative | Saliva — licking a wound, or wetting a cloth or a tissue with it. Human mouth flora is dense and includes organisms that cause nasty soft-tissue infections. This is a folk habit with a genuine downside |
| Leaving it uncovered and clean until you can cover it properly | Any cloth of unknown origin pressed on and left — a rag, a towel from a gym bag, a handkerchief |
| Cling film, if you happen to have it, as a temporary cover for a large graze | Blowing on it to cool or dry it, which is saliva by another route |
Air drying deserves a sentence of its own, because people treat it as a failure. If you have irrigated a wound and have nothing clean to dry it with, letting it air dry for a minute is entirely acceptable and considerably better than patting it with something questionable. The instinct to dry it with something is where a clean wound most often gets contaminated.
3. In a school
- Gloves, then irrigate at a tap, then a sterile non-adherent dressing. The medical room has running water, and it is better than the saline pods for anything gritty simply because there is more of it.
- Saline pods are for eyes and for topping up, not for cleaning a knee. A 20 ml pod does not have the volume to clean a playground graze.
- Record it. Mechanism, what was done, and what the wound looked like. A wound that later becomes infected, or a mechanism that does not match the account, both become questions later — and the second is a safeguarding matter.
- Check tetanus status for anything deeper than a graze, particularly if it involved soil, and for any puncture or bite. UK childhood immunisation covers most pupils, but "most" is not a record.
- Do not use antiseptic wipes as the cleaning step. They are for the skin around the wound. A single small wipe cannot irrigate anything.
4. At home, and afterwards
- Cover it, and keep it slightly moist rather than letting it scab hard. Moist wound healing is faster and scars less than the dry-scab approach most people were taught. A simple non-adherent dressing or a hydrocolloid does this.
- Change the dressing when it is dirty, wet or lifting — not daily by routine, which disturbs healing.
- Steri-strips or skin glue for a clean, straight, shallow cut whose edges come together easily. Not for anything gaping, deep, over a joint, or bleeding through.
- Do not use cotton wool directly on a wound — the fibres stick and come away with the healing surface.
When it stops being a first aid problem
- It will not stop bleeding after 10 minutes of firm continuous pressure.
- It gapes, or you can see fat, muscle or bone. Anything needing stitches is best closed within a few hours — wounds seen late are often left open deliberately.
- Anything embedded that irrigation did not remove.
- Bites — animal or human. Human bites are the higher-risk of the two, and a knuckle wound from a punch to a mouth is a hand infection until proven otherwise.
- Punctures, which look trivial and inoculate deep. Needles, nails, garden forks, sea urchins.
- Hands, face, joints or genitals, where function and appearance are at stake.
- Anything heavily contaminated — soil, manure, sewage, water sports.
- Numbness, weakness, or an inability to move the part beyond it, which suggests nerve or tendon injury and is easy to miss in a wound that looks small.
- Diabetes, immunosuppression, poor circulation, or anticoagulants.
- Spreading redness, increasing pain after day two, pus, fever, or a red line tracking up the limb — that last one is same-day.
One myth worth naming because it persists. Wounds do not need to "breathe". Leaving a wound uncovered to dry out is slower and scars more than keeping it covered and moist. The advice comes from a period before modern dressings and has outlived the reason for it.