You may have heard the news this week 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 body, and 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 colours. The skin is formed by billions of cells, and has many important functions like
regulating temperature, protecting us from germs, and 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 that are 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. So, these skin receptors are there
to detect any sensation, pleasant like a warm bath, or abnormal situation like burning oil.
We all know that our skin is able to detect temperature very precisely, things that are warm,
hot, very hot or super hot. Our skin is able to do this because these
neurons have receptors in their membrane. But until 20 years ago, nobody had any idea
of how these receptors look like, or how are they 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 receptor used capsaicin to find it. Capsaicin has been used in culinary and for its
medicinal properties for more than 4,000 years. Capsaicin is a substance found in hot pepper.
If you ever tried it you might remember the burning sensation in your mouth,
sweat in 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 will
overreact and send messages to the neuron to cause inflammation in an attempt 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, in an attempt to put out the fire. That is why the person will
sweat in the 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 by 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 keep using it 4 times a day until their pain condition is resolved.
If the area of the skin that they need to apply capsaicin is too large, then 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 mostly for hand,
feet, ankle and knee arthritis. We don’t recommend applying to more than 2 areas,
so you may choose two areas that are most painful, this is to limit the amount of capsaicin that will
be absorbed by your body. There are scientific studies showing that the benefits in terms of
pain relief were like the application of topical anti-inflammatories or NSAIDs.
It is also good 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 useful 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.
Now, I’ll explain when you should NOT use capsaicin.
Before, let me remind you that this video 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.
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Capsaicin should not be applied if there is any skin wound, if the skin is irritated
or on membranes like the eyes, mouth or genitals. As I mentioned before, 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 because they may be reactive or allergic.
Talk to your doctor or your pharmacist about it. Usually, these skin irritations
diminish with continued use. 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 any form of heat to the skin before or immediately after the application.
So, no heating pad, hot water or bath in the area. Watch my next video here.
Thank you for watching Goodbye.