Why Do We Itch?
Have you ever wondered why we itch when we have a rash? Or why it feels so good to scratch an itch? The sensation is known as pruritus and is typically caused by irritation of the skin cells or nerve cells associated with the skin. We’re here to give you the details on those annoying itches!
What is Itchiness (Pruritus)?
Pruritus, or itchiness, is an important sensory and self-protective mechanism. Just like pain, vibration, cold and heat. It alerts us to harmful effects on our skin but it can become unbearable if untreated. So much so, that we have many articles addressing your concerns on itchy red skin and spots.
Itching (pruritus) is linked to the brain in the same way that pain is. For pain our reflex is to withdraw or move away. With itching, we feel compelled to scratch. This is a reflexive, protective response developed to help us remove parasites from our skin. Animals also have this sensation. This is why you might find yourself scratching if there’s even a slight movement of your hair. Ultimately, itching is a protective measure we take to protect our skin.
What causes itching?
Many things can cause itching, but usually it’s triggered by histamine. This is a chemical in the body associated with immune responses. It’s histamine that causes the itchiness and redness you will see from bites, rashes and skin dryness.
Here’s a breakdown on some of the most common types of itches you might experience:
Pruriceptive Itch: This is due to an allergic reaction, inflammation, dryness or other skin damage. You’ll experience this kind of itch with:
Neuropathic Itch: This is caused by damage to the nervous system. Usually, it’s combined with numbness and tingling. Shingles, a stroke, or burn injury may cause this type of itch.
Psychogenic Itch: This is caused by a response to serotonin and norepinephrine.These chemicals influence stress, depression and delusional parasitosis – a false feeling of parasite infestation that can cause us to itch.
Why does scratching feel so good?
Hopefully, by now we have a pretty good grasp on the concept of itching. It is typically caused by histamine as an immune response. It is a self-protective measure that our body takes to protect us from parasites or anything harmful to the skin for that matter.
That all makes sense, and even explains why we scratch, but it doesn’t explain why it feels so good! The reason that scratching is so satisfying all comes down to our brain signals. When we scratch it causes a low-level pain signal to shoot up to the brain and override the itch signal – this provides us with temporary relief. Even pinching, slapping or rubbing the itchy spot can work too.
Unfortunately, however, scratching comes with a cost. Some of the chemicals that relieve us of our itch, such as serotonin, can make it easier for the itch signal to be re-triggered. This is why you might notice that scratching can make you itchier, and trigger what scientists call the itch-scratch cycle.
In all, what can we take from this? Itching is a natural phenomenon, designed to protect our skin. There are various causes, but it’s typically due to histamine production as a result of a rash, reaction or bite. Scratching feels amazing and this is due to us overriding the scratch receptor with a pain receptor. It feels good, but can cause more damage than it’s worth. If you’re looking for advice on treating your rash we have plenty of content for you to take a look at.
We would also recommend you establish what kind of rash you have before looking at suitable treatments. Our AI skin image search can help you better understand your skin, and our board-certified dermatologists can give you clear advice on best practice.
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Specialist doctor from the University Hospital in Gothenburg, alumnus UC Berkeley. My doctoral dissertation is about Digital Health and I have published 5 scientific articles in teledermatology and artificial intelligence.