No one likes being cold, so heat therapy sounds good to most people. Now you might ask, how do I know if I should use cold rather than heat? If you’re wondering the same, you are not alone. We get asked that exact question on a daily basis. Let us explain the spectrum of thermal therapy and the use of heat in tissue healing.

Cold and heat therapy do have some benefits in common, but most of the time have opposite effects. Both can relieve pain and muscle spasm, but that’s where the resemblance stops. Hot packs enhance blood flow and metabolism, whereas an ice pack causes both to lower. Cold therapy has a positive effect on swelling, but heat makes swelling worse.

Hot and cold therapy also have similar advantages, like affordability, easy to find, and easy to use. The trick is knowing which one to use but, to answer that question, you need to know which effect you want. Our physiotherapists can help you determine whether your problem needs heat therapy or not and, more importantly, we can teach you how to use it safely.

What exactly is heat therapy?

Heat therapy is exactly what the name sounds like – applying heat to get a therapeutic effect. When a hot pack of other heating modality is applied to your skin, the conduction of thermal energy causes a physiological response in the area. This response includes increased blood flow, leading to redness of your skin. The increased blood flow ensures that more nutrients and oxygen are delivered to the tissues. As a treatment modality, this helps with relaxation of the tissue and can also encourage healing. This superficial heat only penetrates 1-3cm, so heat therapy is less useful for deep pain like hip osteoarthritis. However, it can help to relieve the associated muscle pain and spasm, which helps you to move better and eases a spasm surrounding an injured joint.

Why we use heat therapy:

Heat therapy isn’t a very effective tool on its own, but can be a useful part of treatment to make other techniques and modalities more effective. For instance, heat helps to relieve muscle tension, helping us to get rid of muscle guarding that’s protecting an injured ligament, tendon and especially joints. This prepares the muscles for soft tissue, joint mobilization or nerve mobilization techniques.

Hot packs also helps with pain relief. With an increase in blood flow to the area waste products and pain stimulating chemicals can be transported away from the site of injury.

Heat therapy works by overloading the thermal receptors to bombard your brain with a more serious warning – heat. The pain impulses is like a car speeding towards your brain, and the heat therapy is like setting up a tollgate that slows down the speed of traffic. No, it won’t numb the pain, but definitely eases it for a short while.

Therapeutic effects of heat include:
  • Eases pain
  • Enhance cellular metabolism
  • Promote blood supply to injured tissue
  • Gain tissue flexibility
  • Decrease muscle spasm
  • Relieves joint stiffness

“Hotter is not always better.”

Application of heat therapy

Before applying heat during treatment, your physiotherapist will assess and diagnose your problem to determine if heat therapy is appropriate for your condition. All metal or jewelry in the area should be removed, otherwise these items also heats up and can cause burns to your skin. Certain hot packs, like the microwavable kind, have a protective covering and is placed directly onto your skin. The hot packs used in most physiotherapy practices are heated using hot water, so these wouldn’t be placed directly onto skin. Instead, the hot pack and area is covered by towels.

Always inform the medical professional treating you if you feel anything more than a comfortable heat. If you feel more than this level of heat, you risk burning. Your physiotherapist won’t necessarily remove the heat, but can add another layer of towels to decrease the intensity of the heat therapy. The heat therapy is done at a comfortable temperature – for you.

It’s safer not to apply heat when you’ve lost some feeling in the area like numb patch, even abnormal sensation like pins and needles is dangerous as you may not even notice your skin is burning. Dealing with blisters may just intensity the pain, so be careful and make sure you check your skin regularly. That’s what we do in the practice.

Different types of heat therapy

Hot packs

Paraffin wax


Infrared lamps

Whirlpool or contrast bath

Other forms of heat therapy include towels, sunlight, saunas, heat wraps, and steam rooms.

Physiological changes:


Your heart and all the blood vessels in your body are connected to form your cardiovascular system. This may seem simple enough, but keeping your heart rate and blood pressure regulated is actually quite complex. Luckily, your body has built in mechanisms to keep everything balanced. One of these mechanisms is called vasodilation. Vasodilation is when blood vessels widen to allow more blood flow. Think of the resistance through a thin straw compared to a thick one. Vasodilation happens in response to various things, but with heat it is a protective response to prevent tissue damage. The increased blood flow uses convection to help you cool down. When we apply heat during as a therapeutic modality, this improved blood flow not only brings more oxygen and nutrients to the area, but also enhances the removal of waste products. Cells in your blood that promote healing, like neutrophils and fibroblasts, can also be transported to the area more efficiently.

Pain modulation

Applying heat is also useful for pain control through a couple of mechanisms.

Heat therapy triggers special thermoreceptors in your skin. These receptors are activated by changes in temperature. When these special sensors are activated, it sends a message to your brain about the temperature change which can temporarily block signals from other receptors.

Another benefit of therapeutic heat is muscle relaxation. Vasodilation stimulates the release of certain hormones and also affects the sensitivity of nerves in the area to help relieve muscle spasm. This is especially useful if muscle spasm is a major contributor to your pain and hindering tissue recovery.

What should I feel during heat therapy?

During heat therapy you should only feel a comfortable level of heat, evenly distributed over the area being treated. There shouldn’t be any areas where the heat feels more intense or concentrated. You will feel some pressure from the weight of the hot pack, but also spread out evenly over the area. If you notice any discomfort, either from heat or pressure, be sure to let your physiotherapist know.

You won’t be left unattended during a heat treatment and the medical professional will also check the treated area for excessive redness or sweating. Be sure to report any other signs like dizziness or feeling faint. Heat therapy is very safe if applied correctly and physiotherapists know what to do if you experience adverse effects.

How long does heat therapy take?

There are no fixed times for the application of heat therapy. With some types of heat therapy, like microwaveable hot packs, the application time is automatically limited as the hot pack cools down. When used as a treatment modality during your physiotherapy session, a hot pack can be applied between 5 to 15 minutes, depending on your condition and the treatment goals of that day. Usually it’s used while treating another area.

Be very careful when using electric heating pads or hot packs at home. These devices stay warm until it is switched off or the battery runs out. This means that there is a very real risk of suffering burns, especially if you fall asleep without switching the hot pack or heating pad off. Water bottles may leak and burst, so be careful when using heat on your skin. Incorrect application of a heat therapy at home can lead to first- or second degree burns.

How many times should heat therapy by applied?

Heat therapy is a passive treatment modality and many treatment sessions won’t include any form of heat therapy. This is because active treatment techniques have been proven to be much more effective when treating painful conditions. However, this doesn’t mean that you should throw away all your hot packs or hot water bottles. Even though it won’t solve your problem, heat can still be a useful and versatile tool – in the right circumstances.

A big advantage of heat therapy is that it can be used at home in between physiotherapy sessions. In this case it is mainly used to modify pain, so you can use a hot pack as often as necessary at home. Just remember to check the skin surface where you applied the hot pack after every use or ask someone at home to check it for you if you can’t see the area properly. If there are any signs of blisters or uneven red marks you should stop using the hot pack immediately and ask a medical professional for advice. These signs usually appear when the temperature of the hot pack was too high or with prolonged use.

What can I do at home to make heat therapy more effective?

Even though heat therapy can be a useful part of treatment, it only has a temporary, superficial effect. Your physiotherapist looks at the bigger picture and will explain the possible causes of your pain. We want to use all the tools at our disposal to promote healing, this is an easy way you can help with the healing.

With physiotherapy treatment, it is important to complete the whole treatment plan, especially rehabilitation and conditioning. This is the best way to get long-lasting results.

There are a few things you can do at home:

  • Only apply heat or ice according to your physios advice
  • Do your prescribed home exercises
  • Listen to your body – if the hot pack feels too hot, it is too hot
  • Never lie on top of a heating device (The pressure interferes with your blood circulation which increases your risk of burning)
  • Do not fall asleep while using a hot pack
  • Keep an eye on the condition of your skin

Cost of heat therapy

There is a specific medical aid rate for heat therapy, but a hot pack will never be a major part of your treatment session. Your physiotherapist might use heat therapy to modify pain of make other techniques more effective. This means that you will never be paying only for heat therapy. The effect of a hot pack is only temporary, so we will always use it in conjunction with other modalities to help you get long-term results.

Yes, thermal therapy has its benefits, but there’s just so much more we can do for you.

Medical Aid Code – 001

The medical aid treatment code for heat therapy is 001. This code applies to various forms of heat therapy, including hot packs, infrared and wax therapy. Most medical aids offer re-imbursement for heat therapy.

Does it make a difference to have an experienced physiotherapist apply heat therapy?

A physiotherapist’s skill lies in assessing, diagnosing and treating nerve-, muscle- and joint injuries. Experience and skill makes all the difference to choose the right treatment modalities for your problem. If heat therapy is used during treatment you can be certain that it is applied as part of a full treatment plan with your specific condition in mind. You will see the difference in results when heat is part of a complete treatment package from a physiotherapist versus when it is used at home on its own.

Our physiotherapists have years of clinical experience and in depth knowledge of your body’s anatomy. We understand different painful conditions and injuries and know exactly which modalities to use (or avoid) to help you heal, in as short a time as possible. Thermal therapy is but one of many tools we use to magnify the healing effect.

Heat therapy should not be used:

  • Inflammation

  • Acute injuries

  • Malignant tumours

  • Altered sensation in the area

  • Blood clots in the area

  • Impaired understanding or communication with the patient

Conditions where heat should be applied with care:

  • Pregnancy

  • Problems with blood circulation

  • Swelling

  • Heart conditions

  • Metal in the area being treated

  • Open wounds or recent bleeding

Frequently asked questions about heat therapy:

No. Heat can actually make inflammation worse.

Yes, there can be if heat is applied to certain areas or conditions. There is also a risk of burning if heat isn’t applied correctly.

No. Laser therapy emits very little to no heat.

No. The use of heat therapy depends on your diagnosis, phase of healing and goals of the treatment on that day.

No. Hotter is definitely not better when it comes to heat therapy. If it feels like a hot pack is burning your skin, it is burning your skin and you should remove it immediately.

Well Health Pro - Medical Professionals iPad Favicon