Why You Should Always Use a Sterile Pad with Cold Therapy
Written by Supply Physical Therapy · Reviewed by Dr. Dina Khentigan, DNP · Oct 20, 2026
A cold therapy machine is one of the best tools you can have at home after knee, shoulder, hip or ankle surgery. But the pad on that machine is too cold to sit directly on your skin. The piece that makes it safe is small, cheap and easy to forget: a sterile dressing or skin barrier between the pad and your skin.
This guide explains what that barrier does, why it matters, when you need a sterile dressing versus a non-sterile skin barrier, and how to avoid an "ice burn" while you recover.
Key takeaways
- Never put a cold therapy pad on bare skin. Cold therapy machine instructions warn that the pad alone is too cold to touch skin, and that no part of the pad should touch skin.
- A barrier does three jobs: it prevents cold injury (ice burns), keeps condensation off your skin, and keeps a clean layer over your surgical site.
- Use a sterile dressing over a fresh incision. Use a non-sterile skin barrier over intact skin or over the bandage your surgeon put on.
- Follow your surgeon's schedule, take breaks, and check the skin under the pad every 1 to 2 hours.
- Stop right away if the skin looks pale, waxy, blistered or discolored, or if it burns or goes numb.
What is a sterile pad for cold therapy?
A sterile pad (also called a sterile dressing or polar dressing) is a thin, single-use layer that attaches to the skin side of your cold therapy pad. It sits between the cold pad and your skin. Sterile dressings come sealed and sterile, so they can go directly over a fresh surgical incision.
A non-sterile skin barrier does the same insulating job, but it isn't sterile. It's made for intact skin, or for use over the bandage your surgeon already put on. Ours are cut to fit specific pads and have adhesive strips so they stay in place.
Each dressing or barrier is shaped for a specific pad. A knee dressing fits the knee pad, a shoulder dressing fits the shoulder pad, and so on. That's why the part number matters when you order.
Watch how a sterile dressing works: Prevent Frostbite and Skin Damage: Always Use a Sterile Dressing to Protect Your Skin (Movement Health by Supply Physical Therapy).
Why you should never skip the barrier
1. It prevents ice burns (cold injury)
An "ice burn" is a localized freezing injury. It's essentially superficial frostbite, caused by a cold source held against the skin for too long. The mechanism is the same as frostbite outdoors: ice crystals form in the tissue, damage cell membranes and reduce blood flow to the area.
Cold therapy machines are strong. Manufacturer instructions warn that these units can be cold enough to cause serious injury, including full skin necrosis (skin death), and that the pad alone is too cold to be applied directly to the skin. The barrier adds the insulation that keeps the cold therapeutic instead of damaging.
The tricky part is that freezing tissue goes numb. As Dr. Dina Khentigan, DNP, explains, because frozen or freezing tissue loses sensation, you may not feel the damage while it's happening. That's why a barrier and regular skin checks matter more than how the cold "feels."
2. It keeps moisture off your skin
Cold water running through the pad causes condensation on its surface. If that moisture sits against your skin for hours, it can cause maceration: the skin gets soft, white and wrinkled and breaks down more easily. Wet skin also freezes faster than dry skin.
A dressing or barrier keeps condensation off your skin. Manufacturer instructions also say to stop if the barrier itself gets wet and swap in a dry one before you start again.
3. It protects your incision
In the first days after surgery, your incision is a way in for bacteria. A cold therapy pad is reused for days or weeks and isn't sterile. A sterile dressing puts a clean, single-use layer between the pad and the surgical site, which is why many surgeons ask patients to bring one to surgery or apply one at the first dressing change.
How to prevent ice burns: guidance from Dr. Dina Khentigan, DNP
Preventing cold injury comes down to never putting a cold source directly on bare skin, limiting contact time, and protecting skin that's numb or at risk.
- Limit the time. The universal protocol for ice is 20 minutes on, 20 minutes off. That applies to ice packs, gel packs and cold therapy machines. Let your skin warm back up during the 20 minutes off before you start again, and follow any different schedule your surgeon gives you. Long, uninterrupted contact is the main cause of injury.
- Watch for warning signs and stop early. Numbness, pale or waxy skin, or a burning or aching feeling means injury may be starting. Remove the pad right away. Catching it early (frostnip) is what keeps it from getting worse.
- Protect skin with poor circulation or less feeling. People with neuropathy, peripheral vascular disease, or reduced alertness (for example, after anesthesia or on pain medication) can't always feel or report early injury. Check these areas more often and shorten sessions.
- Keep it dry and don't over-tighten. Wet skin freezes faster. Strapping a cold source down too tightly increases contact and can restrict blood flow. Snug the straps, but don't crank them down.
These steps follow the same principles as the Wilderness Medical Society's frostbite prevention guidelines: limit exposure time, avoid moisture, keep cold (and heat) devices off bare skin, and deal with numb areas right away.
Who is at higher risk of cold injury?
Anyone can get an ice burn, but the risk is higher if you:
- Have diabetes or peripheral neuropathy (reduced feeling in the skin)
- Have peripheral vascular disease or other circulation problems
- Have had a nerve block or are numb after surgery
- Are drowsy from anesthesia, pain medication or sleep aids (many injuries happen when people fall asleep with the pad running)
- Are an older adult or have thin, fragile skin
- Have a history of cold sensitivity, such as Raynaud's phenomenon
- Are very lean over the treated area, so there's less tissue between skin and the pad
Cold therapy machine instructions ask you to give your healthcare provider a full medical history, including any past reactions to cold, before you use the machine, because some conditions make cold injury more likely. If any of these apply to you, ask your surgeon how long and how often you should use cold therapy, and check your skin more often.
Sterile dressing or non-sterile skin barrier: which do you need?
Use a sterile dressing when the pad goes over a fresh incision or open wound. It comes sealed and sterile, so it's safe directly over the surgical site. Many surgeons ask patients to bring one on surgery day. Sterile dressings are single-use, and because they're medical supplies, they can't be returned once purchased.
Use a non-sterile skin barrier over intact skin, or over the bandage your surgeon applied. It gives the same layer of cold and moisture protection, it's much more convenient than a T-shirt or towel, and it's significantly cheaper than a sterile dressing. A T-shirt or towel can bunch up, slide around, get damp and isn't shaped to the pad. Our barriers are cut to fit the pad and stick in place with adhesive strips.
If a dressing doesn't completely cover the skin under the pad, add another barrier. No part of the pad should touch skin.
Find the right one for your machine
Sterile dressings and skin barriers are shaped to fit specific pads, so the right one depends on your cold therapy machine and which pad you're using (knee, shoulder, hip, back and so on). We carry both for the most common cold therapy machines:
Not sure which one fits your pad? Call us at (844) 505-8144 or email CS@supplypt.com and we'll match it for you.
Safe-use checklist for cold therapy at home
- Get your schedule from your surgeon. Know how long each session should be, how long the breaks are, and how many days to keep going.
- Put the barrier on first. Attach a sterile dressing (over a fresh incision) or a non-sterile skin barrier (over intact skin or a bandage) to the skin side of the pad. Make sure no part of the pad touches skin.
- Strap it snug, not tight. Over-tight straps press the cold harder into the skin and can reduce blood flow.
- Check your skin every 1 to 2 hours. Lift the edge of the pad and look. If a brace, cast or wrap makes it impossible to check, don't use the machine without asking your provider.
- Follow 20 on, 20 off. Run the cold for 20 minutes, then give your skin 20 minutes off before the next session, unless your surgeon says otherwise.
- Keep it dry. If the dressing or barrier gets damp, stop and swap in a dry one.
- Be careful at night. Ask your surgeon before running the machine while you sleep. Pain medication and sleep make it harder to notice early injury.
- Stop and call your provider if you notice more pain, burning, swelling, itching, blisters, redness, pale or waxy skin, discoloration or welts.
To keep your cooler cold longer with less mess, see our Ice Freeze Bags.
Frequently asked questions
Do I really need a sterile pad for my cold therapy machine?
You always need a barrier between the pad and your skin. You need a sterile dressing specifically when the pad will sit over a fresh incision or open wound. Over intact skin or over your surgical bandage, a non-sterile skin barrier works.
Can I put a cold therapy pad directly on my skin?
No. Cold therapy machine instructions warn that the pad alone is too cold to touch skin and that no part of the pad should touch skin. Direct contact can cause frostbite and, in serious cases, skin necrosis.
What is an ice burn?
An ice burn is a localized freezing injury, essentially superficial frostbite. It happens when a cold source stays on the skin too long. Ice crystals form in the tissue, damage cells and cut blood flow. Early signs include numbness, pale or waxy skin, and a burning or aching feeling.
What's the difference between a sterile dressing and a non-sterile skin barrier?
Both insulate your skin from the cold and keep condensation off. A sterile dressing is sealed and sterile, so it can go directly over a fresh incision. A non-sterile barrier is for intact skin or over a bandage, and it's significantly cheaper.
Can I use a T-shirt or towel instead?
A clean, dry layer is better than nothing, but a T-shirt or towel isn't shaped to the pad. It can bunch, slide, leave gaps where the pad touches skin, and get damp from condensation. A fitted skin barrier with adhesive strips is much more convenient and stays in place.
How long can I use a cold therapy machine at a time?
The universal protocol for ice is 20 minutes on and 20 minutes off, whether you're using a cold therapy machine, an ice pack or a gel pack. If your surgeon gives you a different schedule, follow theirs.
How often should I check my skin?
Lift the edge of the pad and look at your skin every 1 to 2 hours, or as your provider tells you. Check more often if you have diabetes, neuropathy, poor circulation, or numbness from a nerve block.
Can I reuse a sterile dressing?
No. Sterile dressings are single-use. Replace it as needed, and right away if it gets wet or soiled.
How do I know which dressing fits my pad?
Each dressing and barrier is shaped for a specific pad on a specific machine, so match it to your machine and pad. Check the part number on your pad, or call us at (844) 505-8144 or email CS@supplypt.com and we'll help you find the right one.
Can I return a sterile dressing?
No. Because they're sterile medical supplies, sterile dressings can't be returned once purchased. Double-check the part number before you order.
