Ice or heat for a bruise? The 48-hour rule
By Margaret Hale, Reunoa EditorialLast updated
The short answer
Use ice first. For the first 24–48 hours, apply a cold pack wrapped in a cloth for up to 15 minutes each hour to slow bleeding under the skin and ease swelling. After about 48 hours, switch to gentle warmth for 10–15 minutes a few times a day to help your body clear the trapped blood. Never put ice or heat directly on thin skin.
It's one of the most common questions after a knock: should I reach for the ice pack or the heating pad? The answer depends on timing.
The 48-hour rule
| First 24–48 hours | After 48 hours | |
|---|---|---|
| Use | Cold | Gentle warmth |
| Why | Narrows blood vessels, slows leaking, eases pain and swelling | Opens vessels, increases circulation to clear trapped blood |
| How | Wrapped cold pack, up to 15 minutes each hour [1] | Warm (not hot) compress, 10–15 minutes, a few times a day |
| Avoid | Ice directly on skin | Heat on a fresh, swelling bruise |
Why cold first?
Right after a knock, damaged capillaries are still leaking. Cold helps them constrict, so less blood escapes and the bruise ends up smaller. MedlinePlus recommends wrapping ice in a clean towel and applying it for up to 15 minutes each hour, and keeping the area raised above the heart if you can [1].
To be fair about the evidence: a systematic review of ice for soft-tissue injuries found few high-quality trials and no proven "best" routine [2]. Still, cold is cheap, low-risk and soothing — and that's why doctors recommend it.
Why warmth later?
Once the bleeding has stopped, the goal changes: help your body remove the pooled blood. Gentle warmth boosts circulation to the area. Using heat too early, though, can open up vessels that are still fragile and make the bruise bigger.
Good cold and warm options at home
| Cold | Warm |
|---|---|
| Bag of frozen peas wrapped in a tea towel — moulds to the arm | Washcloth soaked in warm water and wrung out |
| Soft gel pack kept in the freezer | Microwavable wheat bag, heated briefly and tested on your wrist first |
| Ice cubes in a zip bag, wrapped in a thin cloth | Warm (not hot) shower over the area |
Avoid electric heating pads on thin skin unless they're on the lowest setting and you stay awake while using them.
Extra care for thin skin and blood thinners
- Always use a barrier. Thin, older skin can be injured by direct ice or by heat [3]. Use a thin towel.
- Check the temperature with your other hand, especially if you have diabetes or reduced feeling in your skin.
- Shorter is fine. 10 minutes is enough.
- On a blood thinner? Bruises may be larger [4]. Cold and gentle pressure in the first hours matter even more. Get medical advice for a rapidly swelling bruise, and call 911 after any head injury.
Frequently asked questions
Should I put ice or heat on a bruise?
Ice first. Use a wrapped cold pack for up to 15 minutes each hour during the first 24–48 hours. After that, switch to gentle warmth to help the bruise clear.
How long should I ice a bruise?
Up to 15 minutes at a time, with the ice wrapped in a towel, then take it off. You can repeat this every hour during the first day or two.
Does heat make a bruise worse?
Heat on a fresh bruise, in the first 48 hours, can increase bleeding and swelling. Once the bruise has stopped growing, gentle warmth helps it fade.
Is it too late to ice a bruise after a day?
Cold helps most in the first hours, but it can still ease pain and swelling during the first 48 hours. After that, warmth is more useful.
Sources
- Bruise — MedlinePlus Medical Encyclopedia.
- Bleakley C, et al. The use of ice in the treatment of acute soft-tissue injury: a systematic review of randomized controlled trials. American Journal of Sports Medicine, 2004. PubMed 14754753
- Aging changes in skin — MedlinePlus Medical Encyclopedia.
- Blood Thinners — MedlinePlus (U.S. National Library of Medicine).
General information, not medical advice. Written by the Reunoa editorial team; Reunoa makes Bruise Defense & Repair Serum. See our editorial policy for how we pick sources and keep product mentions fair.