Can hot peppers be used to treat chronic pain?
You may have heard that the 2021 Nobel prize of Medicine was awarded to two scientists who discovered the skin receptors for heat, cold and pressure.
Our skin needs to detect threats to our bodies. These can be in the form of high temperatures, like a fire that could cause burns, or low temperatures that could lead to frostbites and loss of a limb, and also has to be able to detect pressure because too much pressure may cause some injury to our body.
The discovery of the TRPV1 receptor was possible thanks to Capsaicin, a substance found in hot pepper that we use to treat some types of chronic pain.
What is capsaicin? What kind of chronic pain is treated with capsaicin? Does it have some adverse effects?
So, let’s talk about capsaicin today
The skin is the largest organ of our body. It is the protective outer layer that gives us different shapes and colors. The skin is formed by billions of cells and has many vital functions, like regulating temperature and protecting us from germs. It is the organ that interacts with the external environment.
The skin has many layers, the epidermis, dermis and hypodermis. The neurons are here, these thin structures connected to the brain to detect information, like sentinels on guard, and these skin neurons have to inform the brain of what is happening around us. These neurons, once activated, send electrical impulses through the nerves, then they enter the spinal cord, make another connection in the spinal cord and then ascend to the brain.
So, these skin receptors detect any sensation, pleasant like a warm bath, or abnormal situation like burning oil. We all know that our skin can detect temperature very precisely, such as warm, hot, very hot or super hot. Our skin can do this because these neurons have receptors in their membrane.
But until 20 years ago, nobody had any idea of what these receptors look like, or how they are activated, or how we could de-activate them. Not until one of the Nobel prize laureates discovered and named the receptor. The Transient receptor potential cation channel subfamily V member 1 or TRPV1.
It was interesting that the scientist who discovered the TRPV1 used capsaicin to find it. Capsaicin is a substance found in hot pepper. If you have ever tried it, you might remember the burning sensation in your mouth, sweat on your face, and flushing that happens immediately when you have one of these.
When I cook dishes with hot peppers, I have to wear gloves to avoid them from burning my fingers, and I remember one occasion that I didn’t wear gloves, and a little bit of capsaicin remained under my nail. The next day when I was scratching my eye, it was not fun. My eye was burning and then I remembered that I had cut some hot pepper the night before.
Capsaicin doesn’t cause any harm to the skin
It is just the sensation of burning because it activates the TRPV1 receptor, then the neuron sends electrical impulses to the brain and the brain interprets it as if there was a fire injury. Sometimes, the brain overreacts and sends messages to the neuron to cause inflammation to heal the injury. We call this peripheral neurogenic inflammation, and the skin will become temporarily swollen and red.
The brain will also tell the sweat glands in the skin to start releasing water in the region to put out the fire. That is why the person will sweat on their face when they eat hot peppers.
What is interesting about capsaicin is that we use it to treat some forms of chronic pain. I’ll talk about that here.
I already explained to you that when capsaicin, which is a molecule like this, reaches the skin neuron, it will connect with the receptor TRPV1, open the receptor, and then initiate an electrical impulse that will travel to the brain. A single exposure to capsaicin does that; however, if we keep exposing this same neuron to capsaicin, like 4 times a day, for 2 weeks, this neuron will become less sensitive to pain. This is because the neurotransmitter for pain, or substance P, will be used up. And without substance P, there is no pain.
In Canada, we do have topical creams and patches containing low-dose capsaicin. We have two concentrations, 0.025%, and 0.075%. We usually tell the patient to start applying the lower concentration first because they will feel the burn. But if they keep applying, the skin will become less sensitive, and then they can use the higher concentration. But for this treatment to work, they need to apply 4 times a day, and they only start feeling the benefits after a couple of weeks. Then, they need to use it 4 times a day until their pain condition is resolved.
If the area of the skin where they need to apply capsaicin is too large, the treatment becomes impractical and too expensive. So this works for skin areas that are small and easy to access 4 times a day.
We recommend this primarily for hand, feet, ankle, and knee arthritis. We don’t recommend applying to more than 2 areas, so you may choose the two most painful areas. This is to limit the amount of capsaicin that your body will absorb. Scientific studies are showing that the benefits in terms of pain relief are like the application of topical anti-inflammatories or NSAIDs.
It is also suitable for small areas of neuropathic pain, like peripheral nerve entrapment.
In some countries, there is a high concentration patch of 8% capsaicin. And that can only be applied by a doctor in a hospital. It has been helpful for post-herpetic neuralgia. And the patient has to be anesthetized before applying the patch, or they don’t tolerate the acute burning. This patch has to be applied for 60 minutes and the effects usually last 3 months.
When you should NOT use capsaicin
Before, let me remind you that this post is for educational purposes only. If you think you have a condition that requires treatment with capsaicin, please talk to your doctor. If you have an emergency, go to the nearest emergency department or call an ambulance.
Capsaicin should not be applied if there is any skin wound or if the skin is irritated or on membranes like the eyes, mouth, or genitals.
As I mentioned, use gloves or a cotton swab to apply on yourself. And if there is any redness or irritation after using it, maybe you should stop this treatment. Talk to your doctor or your pharmacist about it. Usually, these skin irritations diminish with continued use. But you have to apply 4 times a day to have the benefits. If you stop one day, then the skin irritation may come back the next time you apply capsaicin.
Do not apply heat to the skin before or immediately after the application. So, no heating pad, hot water or bath in the area.
You can watch my video about capsaicin for pain here.
- Andrea -
