Heat or ice for injuries is one of the first questions a patient asks and one of the least settled in the literature. This guide is written for UK physiotherapists, sports therapists, club first aiders and clinic teams who have to answer it in seconds and then defend the answer. It covers what the research actually supports, a decision table organised by hours since onset, sensible application doses, the patients you should screen before applying either, and what to keep in the treatment room.
TL;DR
- Cold belongs in the first 48 to 72 hours after a traumatic soft-tissue injury, and it earns its place on pain relief rather than faster healing.
- Heat belongs with stiffness, muscle spasm and persistent pain where there is no fresh swelling.
- NHS self-care advice for a sprain or strain is an ice pack for up to 20 minutes every 2 to 3 hours across the first 2 to 3 days, and avoiding heat packs for the first couple of days.
- The evidence for ice is thinner than its popularity suggests. A review of 22 randomised trials found no evidence of an optimal mode or duration of treatment.
- Heat has the stronger trial record in low back pain, where a Cochrane review of 9 trials and 1,117 participants found moderate evidence of a small short-term reduction in pain and disability.
- Screen for impaired sensation, poor circulation and cold sensitivity before either modality goes near a patient.
- A reusable pack covers both jobs from £1.10 a pack ex VAT in the box of 28. Instant ice packs need no freezer and work out at 40p an ice pack once you order two boxes or more.
Why the heat or ice question keeps coming back
You answer this more often than almost anything else you get asked, usually while doing something else. It comes from a parent on the touchline, or a patient at reception on their way out. The popular version of the answer is ice for a new injury and heat for an old one, which is roughly right and hides two problems.
The first is that "new" and "old" are carrying a lot of weight. A hamstring strain at three days and the same strain at three weeks are different problems with different answers, and so are a swollen ankle and a stiff, unswollen one. The second problem is the evidence base. Cold therapy is far more popular than its trial record justifies, and that changes how firmly you should recommend it and what you should say when a patient asks whether it will get them back sooner.
This post sits above the rest of our hot and cold material rather than repeating it. For the physiology of vasoconstriction and vasodilation, read the science behind hot and cold therapy. For handling, storage and microwave times there is a separate guide to using hot and cold packs safely, and the at-home best practice guide sets out an alternating cycle you can hand to a patient. If you have already made the call and are picking a format, instant ice packs versus reusable cold packs compares the two. What follows is the decision itself.
What the evidence actually says about ice
The NHS is specific on acute sprains and strains. Its self-care advice is the five steps of PRICE therapy for the first 2 to 3 days, with the ice step written as "apply an ice pack (or a bag of frozen vegetables wrapped in a tea towel) to the injury for up to 20 minutes every 2 to 3 hours". The same page tells patients to "avoid heat (such as hot baths and heat packs), alcohol and massages for the first couple of days" in order to help prevent swelling. That is the clearest public instruction most of your patients will have seen, so it is worth knowing it word for word.
Where cold has never established itself is on healing. Bleakley, McDonough and MacAuley reviewed 22 randomised trials of ice in acute soft-tissue injury for the American Journal of Sports Medicine. They found marginal evidence that ice plus exercise is most effective after ankle sprain and after surgery, little evidence that adding ice to compression had any significant effect, and no evidence of an optimal mode or duration of treatment. Methodological quality across those trials averaged 3.4 out of 10 on the PEDro scale, so the confidence behind routine icing rests more on habit than on strong trials.
Dubois and Esculier pushed the point harder in the British Journal of Sports Medicine in 2019. Their PEACE and LOVE framework succeeds PRICE and POLICE, and the A in PEACE stands for avoid anti-inflammatory modalities. On cold they wrote: "We also question the use of cryotherapy. Despite widespread use among clinicians and the population, there is no high-quality evidence on the efficacy of ice for treating soft-tissue injuries." Their reasoning is that ice, while mostly analgesic, "could potentially disrupt inflammation, angiogenesis and revascularisation".
None of that takes ice off the trolley. It changes the sentence you say out loud. Offer it as pain relief and short-term comfort, not as an accelerant, and do not let a patient sit under a pack instead of loading the tissue. The same editorial caps protection at 1 to 3 days and adds that "rest should be minimised as prolonged rest can compromise tissue strength and quality".
What the evidence says about heat
Heat has the better trial record in one specific place, the low back. A Cochrane review by French and colleagues pooled 9 trials and 1,117 participants and found moderate evidence that heat wrap therapy gives a small short-term reduction in pain and disability in a mix of acute and sub-acute low back pain, with further improvement when exercise is added. The cold evidence in the same review came from only three poor-quality studies, and the authors state that no conclusions can be drawn about the use of cold for low back pain.
NHS self-care advice for back pain reflects that split without spelling it out. It offers both, with a different job written next to each: an ice pack "wrapped in a tea towel to reduce pain and swelling", and a heat pack or hot water bottle "wrapped in a tea towel to relieve joint stiffness or muscle spasms". Those two clauses do most of the deciding for you. Swelling points to cold. Stiffness and spasm point to heat. Most of the confusion in this topic comes from arguing about injury names when the sign in front of you answers the question.
Choosing heat or ice for injuries by hours since onset
The table below puts the two variables together: what the presentation looks like and how long ago it started. Treat it as a starting position that clinical judgement overrides, not a protocol.
| Presentation | Time since onset | Reach for | Dose and caution |
|---|---|---|---|
| Ankle, knee or wrist sprain | 0 to 48 hours | Cold | Up to 20 minutes every 2 to 3 hours, with a tea towel between pack and skin. |
| Ankle, knee or wrist sprain | 48 to 72 hours | Cold while swelling persists | NHS advice is to avoid heat packs across the first couple of days. |
| Ankle, knee or wrist sprain | After 72 hours, swelling settled | Heat before movement work | Use it to ease stiffness ahead of loading, not in place of loading. |
| Muscle strain in the hamstring, calf or quadriceps | 0 to 72 hours | Cold for pain relief only | Protect for 1 to 3 days, then load. Do not promise faster healing. |
| Contusion from a direct blow | 0 to 48 hours | Cold | Same dose. Refer if swelling or bruising is getting worse rather than settling. |
| Non-specific low back pain with no trauma | Any stage | Heat | Moderate evidence for heat wrap therapy in acute and sub-acute presentations. Pair it with exercise. |
| Neck or back muscle spasm | Any stage | Heat | NHS advice lists heat packs for joint stiffness and muscle spasms. |
| Stiff joint with no swelling | Any stage | Heat | Apply before mobility work rather than afterwards. |
| Post-operative joint | As the surgical protocol allows | Cold, combined with exercise | One of the few places the ice evidence is positive. The surgeon's protocol takes priority. |
Two entries in that table are worth pausing on. The sprain row splits three ways because it is the presentation where clinicians most often get stuck, holding a patient on ice into week two when the swelling has long gone and stiffness has become the limiting factor. And the low back row ignores hours since onset entirely, because the trial evidence there is organised around acute and sub-acute categories rather than a clock.
How long should you ice an injury
There is a ceiling with good support behind it and an optimum with none. The ceiling is up to 20 minutes at a time, repeated every 2 to 3 hours across the first 2 to 3 days. The optimum does not exist in the literature: Bleakley's team went looking for an optimal mode and duration across 22 trials and found neither, so any source quoting a precise protocol to the minute has gone beyond what the trials can support.
Twenty minutes is a reasonable working number over a limb with a normal layer of subcutaneous fat, with a tea towel or cloth between the pack and the skin as the NHS advises. Two things should shorten it. Bony, poorly padded areas cool faster than fleshy ones, and superficial nerves run close to the skin at points such as the fibular head and the medial elbow. Bassett and colleagues reported six cases of peripheral nerve injury after ice application in the American Journal of Sports Medicine, all of which resolved spontaneously, and pointed clinicians at three variables: where the major peripheral nerves run, how much fat lies over them, and how long the tissue is cooled.
Heat needs a ceiling for a different reason. A pack that feels comfortable on intact, well-innervated skin can still burn someone who cannot feel it properly, and the classic presentation is a patient who fell asleep on one. Set a timer and check the skin early in the application rather than at the end. Never leave a pack underneath a limb, where body weight traps the heat against the skin.
Can you alternate heat and ice
Contrast therapy has a place, mostly with subacute problems where you want to ease stiffness and then settle any reaction afterwards. It is not a way to shortcut the acute phase. With fresh swelling in front of you, bringing heat in works against the thing you are trying to control, and the NHS position on the first couple of days after a sprain leaves little room for interpretation.
Our at-home guide to hot and cold packs sets out a cycle in enough detail to give a patient. The judgement call worth adding is the endpoint: finish on whichever modality matches the dominant problem, so cold last if swelling is still the issue and heat last if stiffness is. Frame it to the patient as a comfort and mobility strategy, which is all either modality is doing.
Targeted cold has its own uses that a flat pack handles badly. Plantar fascia pain and small foot joints respond better to something you can roll and weight, which is covered in our guide to the cold massage ball.
Who should not have heat or ice
Both modalities are safe for most people, and almost every harm they cause is avoidable. Kunkle and colleagues, reviewing the orthopaedic use of cryotherapy in JBJS Reviews, put it plainly: complications including skin irritation, frostbite, perniosis and peripheral nerve injuries "can be avoided through patient education and reducing the duration of application". The avoidable part is mostly duration, plus the cloth barrier between pack and skin that the NHS asks for.
- Impaired sensation in the area removes the patient's warning system, so neither modality should be left with them unsupervised.
- Cold sensitivity changes the calculation. NHS advice for Raynaud's is to keep the hands and feet warm and to avoid sudden changes in temperature, which makes an ice pack on the extremities a poor first choice.
- Compromised circulation in the limb slows the tissue's ability to recover from either extreme.
- Skin that is broken, infected or already burnt should have nothing applied to it.
- A patient who cannot remove the pack themselves, whether through reduced mobility, cognition or simply falling asleep, needs a supervised application and a timer.
In care home and community settings the first and last points do most of the work, which is a good argument for packs that are applied and removed by staff rather than left with a resident.
The packs that make the decision practical
The decision above is only as good as what is within reach when you make it. Two formats cover almost every scenario, and the split between them is about setting rather than clinical merit.
Meglio Hot and Cold Pack
One pack that goes either way is the sensible default for a fixed treatment room, because you rarely know which way the next patient will need it. Freeze it for the acute presentations in the table, warm it for the stiffness and spasm rows, and put it back for the next patient. It is the format that lets you change your mind halfway through a course of treatment without buying anything else.
Where it falls short is mobility. The gel pack needs a freezer to be cold and a microwave to be hot, so it belongs where there is a plug and a kitchen rather than in a kit bag on an away fixture.
Pricing is £2.49 ex VAT for a single pack, £1.25 a pack ex VAT in the box of 14, and £1.10 a pack ex VAT in the box of 28 at £30.80. For a clinic with more than one treatment room, the box of 28 is the version that lets you keep some in the freezer and some warm at the same time without rationing.
Meglio Instant Ice Pack, box of 25
Squeeze the sides and it turns cold chemically, with no freezer involved. That single property is why it works for clubs, academies and any team treating players away from a base. It answers the acute rows of the table on a touchline where a reusable gel pack would have thawed hours earlier.
The trade-off is that they only go one way. There is no heat setting, no second use, and no help at all with the stiffness and spasm rows. Treat them as the acute-phase consumable rather than a complete hot and cold solution.
A box of 25 is £13.33 ex VAT, which works out at 53p an ice pack, and 40p an ice pack once you order two boxes or more. At that price there is little reason to ration them, and a pack nobody uses because someone is saving it does no good in the bag.
Stocking hot and cold therapy for a clinic or club
The per-unit comparison between the two formats is misleading, because one is a consumable and the other is an asset. An instant pack costs 40p and is gone. A reusable pack costs £1.10 in the box of 28 and comes back out of the freezer next week, so its cost per application falls every time someone uses it. The useful question is what each setting actually needs across a season.
A fixed clinic with a freezer needs reusable packs in quantity and very few instant ones, kept for home visits and the occasional day away. A club or academy running fixtures at other people's grounds needs the reverse, with instant packs as the working stock and a handful of reusable packs at the home base. Community and domiciliary teams sit in the middle, and instant packs do most of the work there, because the freezer is always somewhere else.
If you are building a bag from scratch, our guide to the pitch-side first aid kit covers what sits alongside the cold packs, and there is a wider breakdown of what clinic consumables cost per treatment if you are pricing a room rather than a bag. Everything discussed here sits in the hot and cold therapy range, and taping supplies for the compression side of the acute presentation are covered in how to tape an ankle for support.
FAQs
Should I use heat or ice for injuries in the first 24 hours?
Cold, in almost every traumatic case. NHS self-care advice for a sprain or strain is an ice pack for up to 20 minutes every 2 to 3 hours across the first 2 to 3 days, alongside protection, rest, compression and elevation. The same advice asks patients to avoid heat, hot baths and heat packs over the first couple of days, because heat works against swelling control.
How long should you ice an injury?
Up to 20 minutes at a time is the widely supported ceiling, repeated every 2 to 3 hours in the acute phase. There is no evidence-based optimum below that. A review of 22 randomised trials looked for an optimal mode and duration of cryotherapy and found neither, so precise minute-by-minute protocols are convention rather than evidence.
Can you alternate heat and ice on the same injury?
Yes, once the acute phase has passed and swelling is under control, usually to ease stiffness while managing any reaction afterwards. It is not appropriate while there is fresh swelling, since heat undoes what the cold is there to do. Our at-home guide to hot and cold packs sets out a cycle you can give a patient.
Does ice actually speed up healing?
No good evidence says so. Writing in the British Journal of Sports Medicine, Dubois and Esculier noted there is "no high-quality evidence on the efficacy of ice for treating soft-tissue injuries" and raised the possibility that ice disrupts inflammation, angiogenesis and revascularisation. Ice is defensible for pain relief and comfort. Framing it as an accelerant is not.
Is heat better than ice for back pain?
For non-specific low back pain with no recent trauma, heat has the stronger evidence. A Cochrane review of 9 trials found moderate evidence that heat wrap therapy produces a small short-term reduction in pain and disability, and better results still when exercise is added. The same review could draw no conclusions about cold for low back pain.
What should a club stock with no freezer at the venue?
Instant ice packs, which activate chemically and need nothing but a squeeze. A box of 25 instant ice packs is £13.33 ex VAT, or 40p an ice pack when you order two boxes or more. Keep reusable packs at the home base for stiffness and spasm work, since instant packs cannot deliver heat.
When should hot and cold therapy be avoided entirely?
Avoid both where sensation is impaired, circulation is compromised, or the patient cannot remove the pack themselves without help. Broken, infected or burnt skin rules out any application. Cold needs particular care on the extremities in cold sensitivity conditions, and neither modality should ever sit directly against skin without a cloth barrier.
Getting the call right in front of a patient
The decision comes down to two observations, not a diagnosis. Look for swelling and look at the clock. Fresh swelling from a traumatic event points to cold, capped at 20 minutes and repeated through the first two to three days for pain relief rather than for repair. Stiffness or spasm with no fresh swelling points to heat, and it works best immediately before movement rather than as a substitute for it. Anything you are genuinely unsure about is a case for the safer option, which is a shorter, well-padded application with someone watching the clock.
The part worth changing in most clinics is not the choice but the sentence that goes with it. Once you stop selling ice as something that heals and start using it as something that makes early loading tolerable, the advice gets simpler and the patient stops waiting for the pack to do the work.
This article is intended for qualified healthcare professionals and is not a substitute for clinical training or professional judgement. Always apply evidence-based practice and refer patients to appropriate specialists where required.
