You twisted your ankle at futsal, or you woke up with a neck that won’t turn. You open the freezer, then the drawer with the heat pad, and you stop. Which one?
Two questions settle it: how new is the problem, and is the area swollen or hot to the touch?
The short answer
- Cold for a fresh injury, less than 48–72 hours old, especially with swelling, bruising or warmth: a rolled ankle, a knock, a pulled calf.
- Heat for stiffness, tight muscles and aches that have been around for days, weeks or months: a stiff neck, a tight lower back, morning joint stiffness, period cramps.
If you still can’t tell, use cold. Cold on a stiff muscle feels unpleasant but does little harm. Heat on a fresh, swollen injury can make the swelling worse.
What heat does in your body
Heat opens up the small blood vessels in your skin and the muscle underneath. More blood reaches the area, and tight muscle fibres let go. Your nerves also pick up the warmth, which turns down the pain signal for a while. That is why a heat pad on a tight back feels good within minutes.
For recent back pain without swelling, the evidence supports heat. A Cochrane review found that heat wraps eased pain and helped people move better in the short term for back pain of up to three months.
What cold does in your body
Cold narrows those same blood vessels. Less fluid leaks into the injured tissue, and the cold numbs the area. Its main job is to take the edge off pain in the first few days. Newer sports medicine thinking questions whether ice speeds up healing itself, so treat it as pain relief, not a cure.
The mechanisms side by side: hot compress vs cold compress.
A quick decision table
| Your situation | Use |
|---|---|
| Rolled ankle yesterday, puffy and bruised | Cold |
| Knee knocked on a table, swelling up | Cold |
| Stiff neck after sleeping badly | Heat |
| Lower back tight after a long day at the desk | Heat |
| Back seized up in bed overnight | Heat |
| Knee arthritis, stiff every morning | Heat |
| Arthritis flare, joint hot, red and swollen | Cold |
| Gout flare in the big toe | Cold |
| Knee replacement, first two weeks | Cold |
| Heavy, aching legs with varicose veins | Neither; cool water and elevation |
| Period cramps | Heat |
| Sore legs the day after a hard run | Either; most people prefer heat |
| Old ankle sprain, months ago, still stiff | Heat before exercise |
How to use each one
Cold: wrap an ice pack or a bag of frozen peas in a thin towel. Keep it on for 10–15 minutes, then take it off for at least an hour. Never put ice straight on skin.
Heat: put a towel or cover between the pad and your skin. Start on the lowest setting, use it for 15–20 minutes, then check your skin. Mild pinkness is normal. Blotchy red or white patches, or blisters, mean stop. See how long to use a heating pad for session timing, and “my physio said use heat” — but how, exactly? for the full method.
Your situation, in detail
Back: lower back pain · the first two weeks after it goes · it locks up in bed at night · sciatica · slipped disc · desk work
Neck and shoulders: neck pain and stiffness · woke up unable to turn your head · neck arthritis · shoulder blade · frozen shoulder · tension headache
Joints: knees and joints · knee osteoarthritis · after a knee replacement · stiff hips · hand arthritis · rheumatoid arthritis · gout flares · an old ankle sprain
Hand and wrist: carpal tunnel · thumb and wrist pain from phone use · trigger finger · a stiff wrist after a cast
Everyday aches: period cramps · blocked ducts and mastitis · cold office aircon · muscle knots · stomach ache · chronic pain flare days
Legs and circulation: varicose veins and swollen legs · night cramps in the calf · cold hands and feet
Sport: sore after the gym · Achilles · plantar fasciitis · tennis and golfer’s elbow · badminton, tennis and squash
Don’t use heat if…
- The injury happened in the last 48–72 hours and the area is swollen, bruised or warm. See the 48–72 hour rule.
- You have reduced feeling in the area, for example from diabetes, a stroke or a spinal injury. See heating pads and diabetes and heat pads after a stroke.
- The skin is broken, infected, or has a rash.
- You have a fever, or the area is red, hot and getting worse.
- You’re pregnant and thinking of putting heat on your belly. See heat during pregnancy.
- You’ve just used a heat rub or medicated patch on the area. See deep heat rubs and heating pads.
The full list is in who should not use a heating pad.
See a doctor or physio instead if…
- You can’t put weight on the leg, or the joint looks out of shape.
- You have numbness, pins and needles or weakness spreading down an arm or leg.
- Back pain comes with loss of bladder or bowel control, or numbness around the groin. Go to A&E.
- The pain hasn’t improved after two weeks of looking after it yourself.
Heat and cold ease symptoms. They don’t tell you what’s wrong. If the pain keeps coming back, get it assessed.
Buying a pad, or wondering whether something else suits you better? Start with what a physio looks for in a heating pad.
The heat pad we use
We’ve supplied the Bremed BD7800 since 2010. It holds a steady temperature, covers a whole lower back and has a machine-washable cotton cover. Physiotherapy clinics in Singapore use it with their patients.
Clinically reviewed by: Nigel Chua (Hand Occupational Therapist) & Louise Yow (Physiotherapist). This article is general information, not a diagnosis. electricheatpad.com sells electric heat pads.
