Help I can’t stop itching!
Why is dry skin so unbearably itchy? Have you ever wondered what is happening to your skin and in your brain during the itch?
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This blog takes you on a fascinating dive into the reasons itch-scratch cycle during an eczema flare is so intense it literally becomes an addiction, and what can you do to stop it.
When you can’t stop itching, even if you are doing damage to your skin, it’s not really your fault. You don’t have a lack of will power. The factors at play in your body are very strong, so much so, it becomes an addiction. Yes, itching can become a hardwired physical addiction in people with eczema, all because of a dehydrated skin barrier.
I will explain… Lets take a quick look at why humans itch in the first place, then I will explain what has gone wrong with that process in people with eczema and what you can do about it.
It turns out that Itching is much more of a brain thing that it is a skin thing. Located deep into the most primal areas of our brain, are the reward circuits. The same ones that light up with exposure from lots of things, like sex, chocolate, even cocaine, and itching. Yes, itching makes you feel good….. for a reason.
The normal purpose for this behavior is to motivate you to address something that is wrong, a threat to your skin, like maybe a spider that’s about to bite, or an offending plant you’ve come in contact with. Itching is a protective mechanism.
Your skin is telling your brain you take action with your hands to address the issue, by itching. When you do take action by itching the offender away, the brain will get a dose of chemical reward. It supposed to be a win-win. You take care of your skin, the brain feels good about it, and will continue the behavior next time the need arises.
However, in recent studies, scientists have documented that the brain in eczema patients reacts differently to the sensation and REWARD of an itch and this finding is very telling to why you can’t stop itching
There are two proposed pathways that scientists think are responsible for conveying the urge to itch to the brain. Researchers have observed that people with eczema differ then people without eczema in one of those two pathways. Lets see why that difference makes itching worse for eczema patients.
We need to look at some human brains.
In one very clever study, scientists were interested if people with eczema responded differently in the brain to itching than people who didn’t have eczema. The short answer, yes, yes they did. I just said that.. …BUT WHY? They have no clue. …HOW, is quite telling.
It all began when a group of volunteers were placed in an F-MRI machines, which show what is happening deep in the brain in real time. Of course they were divided into two groups, those with eczema and those without.
Then scientists pricked their skin with histamine, a known chemical our body uses to signal the need to itch. Hitamine activates the “histamine itch response”, and follows pathway number one to the brain. In both groups, their brains responded similarly to the need to itch and both had the pleasure response as expected from the itch. Check, for histamine.
But then, here comes the breakthrough. They next used a prick of a known stinging plant called cowhage. Cowhage and other similar topical stinging irritants signal the itch response by activating pathway number 2..Pathway number two starts with special receptors found in our outer most skin cells, keratinocytes.…. So there are a lot of them and their special receptor is named PAR2. These receptors are unique because they are not activated by touch alone, they are activated by chemical offenders.
When these PAR2 receptors are activated from cowhage, they produce a much stronger reaction than the histamine pathway does. They send signals to the brain on the second proposed pathway leading to the brain to create an itch response. Along the way, they release multiple inflammatory communicators, other than histamine that ramps up the urge to itch.
The evolutionary purpose of this amplification on the pathway number two, is to really get the attention of the brain to address issue located at the skin, the chemical offender.
Its thought that the PAR2 receptors are there to alert the skin to very dangerous threats like poison oak or ivy, not a silly fly or piece of grass on the skin.
In most people the second pathway to the brain bypasses the pleasure response. After all, evolution would not want humans to be rewarded for coming into contact with dangerous plants.
"Just take care of the problem and don’t do it again." ~ says the brain
Some very interesting things were documented in the volunteer brains of all the patients when the cowhage was given? As expected, The people without eczema reported the stinging sensation and Various areas of the brain went to work to address the offending chemical and itch it. What was super cool was that The area closely related to memory also lit up, suggesting that human evolution has responded to help us remember the stinging offender and avoid it next time.
Meanwhile, back to itching, the FMRI’s of the eczema patients told a different story. While the usual pathways lit up, including the memory part from the cowhage prick.
Something very strange occurred that help piece together this itchy puzzle.
When the cowhage was applied, only in the eczema patients, the pleasure center activated. This isn’t supposed to happen. This means that in people with eczema, when the second pathway to the brain used by the attention getting PAR2 receptors, the process makes a mistake and rewards the brain. Instead of avoiding the offender, the brain gets a pleasure cue. Setting the stage for self destructive itching.
But wait… there’s more. people with eczema tend to have a lot of odd things going on with their keratinocytes, the cells in the outer skin barrier… yup, its happening again, involving the PAR2 receptors. In people with eczema, Not only does the brain overreact and provide pleasure when PAR2 receptors are stimulated, it has also been documented that people with eczema tend to have a lot more of these PAR2 receptors in their keratinocytes than people without eczema. So its a double whammy of to the itch-scratch cycle. More PAR2 receptors and pleasure from them.
Geneticists haven’t figured out the cause of that observation just yet, but the implication is clear as day. Not only do people with eczema have a strong addicting response to itching, they have more receptors in their skin to trigger it.
To make matters worse People with eczema can become super sensitive to external triggers, producing an uncontrollable itching response.
This is why a ‘flare’ journal is often recommended by doctors.. did you come into contact with anything new or different 24-48 hours? If you can find that link, then you can take control of this aspect of your eczema. If your body has become sensitized to something, knowing what it is and avoiding can go a long ways preventing the itch-scratch cycle from starting and leading to a flare.
Okay, well that’s what’s going on the outside. What if you live in a bubble and nothing new touched your skin… yet you are still itchy?
That is where we circle back the dry skin connection… something all eczema patients have in common.
Scientist turned to rats here to help figure out why we itch dry skin. They took a group of rats, shaved their backs, and applied acetone to their skin…
this creates dry skin because it dissolves away the (oils) that hold the skin barrier together… instantly causing water loss and dry skin.
And instantly creating itchy rats.
What researchers observed was that there was a large release of histamine in the rats epidermal tissue. We discussed earlier that histamine stimulates one of the two main pathways to cause an itch sensation. So no surprise there.
Then the scientists took it a step further, and genetically engineered the rats to be void of histamine. No histamine, anywhere in their bodies, they preformed the same experiment with acetone on the shaved rats, and they were still itching…. Even without histamine
It turns out, when cells become ‘structurally deflated’ aka dehydrated, they also release cytokines which are chemical communicators that stimulate the other nerve pathway…. Wait for it…the same pathway to the brain that PAR2 receptors use. This pathway was supposed to be just for dangerous chemicals with surface contact.
Side note: In case you are wondering, we know that acetone does not stimulate the PAR2 receptors, its not a direct irritant like cowhage, therefore the stimulation of the PAR2 pathway was from something other than acetone in this experiment…..
What happened was when the skin cells released their cytokines, in distress from becoming deflated, their chemical messengers took the second pathway to the brain, the PAR2 pathway, which we know gets a very strong addicting reaction.
Therefore, because your brain is wired differently, chronic dry skin from eczema is constantly stimulating your brain in very powerful addicting ways that keep you itching, even if it is causing obvious harm.
Now you know, that’s why you keep itching even if your skin is raw and injured.
So what can you do about it?
First, obviously Keep away from things that aggravate your skin.
But most importantly of all, really, really focus on keeping your skin moisturized. If you do notice that you have an area of skin that is getting itchy, apply an occlusive moisturizer that will seal in water and lipids, you can even place a wrap on it overnight to force in the moisture and help stop the histamine and cytokine release. You can break the itch cycle in the skin by moisturizing.
I’d look for moisturizers that are specifically formulated for eczema patients because not all lotions are good for protecting the skin barrier.
Many lotions are formulated to bypass the skin barrier and carry other active ingredients deep into the skin. You want the opposite, you need a cream that will sit on the surface and protect it. These moisturizers should be thick and probably not absorb all the way. These will be the ones to turn to when an area gets itchy. In order To avoid the itch in the first place, take care of your skin barrier by having good hygiene, avoid irritants, and lightly moisturize, moisturize, moisturize, on a daily basis.
1. PAR receptors
Akiyama, T., Lerner, E. A., & Carstens, E. (2015). Protease-activated receptors and itch. Handbook of experimental pharmacology, 226, 219–235. https://doi.org/10.1007/978-3-662-44605-8_13
2. FMRI during Itch response
Article Source: Brain’s Reward Circuits Mediate Itch Relief. A Functional MRI Study of Active Scratching
Papoiu ADP, Nattkemper LA, Sanders KM, Kraft RA, Chan YH, et al. (2013) Brain’s Reward Circuits Mediate Itch Relief. A Functional MRI Study of Active Scratching. PLOS ONE 8(12): e82389. https://doi.org/10.1371/journal.pone.0082389
3. Rats Itching with dry skin
Mechanisms and Management of Itch in Dry Skin
Catharina Sagita Moniaga1, Mitsutoshi Tominaga1,2 and Kenji Takamori1–3,
. Juntendo Itch Research Center (JIRC), Institute for Environmental and Gender Specific Medicine, 2Anti-aging Skin Research Laboratory, Juntendo University Graduate School of Medicine, and 3Department of Dermatology, Juntendo University Urayasu Hospital, Chiba, Japan
Accepted Oct 15, 2019; Published Jan 9, 2020