Introduction
As the title goes, you might wonder why do we scratch so much. Chances are, you will be scratching right now! We all itch subconsciously to get relief from the invisible disturbances on our skin. This in turn takes over your mind for several minutes. One story goes where a woman in her 30’s had a habit of scratching through her scalps during her sleep time at night. One night this got intensified and the next day morning she woke up to find green slimy liquid on top of her hair. When she went to the hospital to know what she has got into, she was immediately admitted to the emergency unit. What happened was she scratched her way all through her scalp to her brain, the green slimy liquid was actually her brain tissues.
The skin
To explain this, let’s start with our first line of defense: the skin. Our skin absorbing all the pressure and shocks coming externally is made up of 1000’s of tiny receptors to recognize pain, pressure, touch, itch, etc. The largest organ in our body taking 16% of our body weight stretches 1.7 m2 when laid our flat. It’s the foundation for the integumentary system which is an organ system consisting of the skin, hair, nails and exocrine gland.
Evolution of itching
The medical term for itching is pruritus. Samuel Hafenreffer was a German physician, who in 1660 introduced the definition of pruritus. Pruritus is the "unpleasant sensation" the body produces that provokes a person to itch themselves. Hafenreffer is also credited as being the author of the first textbook on the subject of dermatology.
Evolutionarily we evolved our itch mechanism to rid ourselves of disease-causing insects and plant matter. But very little evidence suggests that scratching gives any immunity benefits. When some flies, bugs, insects come in contact with our skin, we start scratching. Seeing us scratch the people around us also start scratching. This might be the evolution's way of letting others know: the bugs which infested us are probably around here and might infect you also, so start scratching to defend yourself. Ever wondered you don’t scratch the areas of skin when the skin is in pain. This might be because during pain, the receptors stimuli a wide range of neurons to inhibit the ich receptors thereby suppressing the urge to scratch.
Approximately 280 million people globally, 4% of the population, have difficulty with itchiness. This is comparable to the 2–3% of the population suffering from psoriasis.
Skin Irritations
The other ways of skin irritation are through fungal infection, allergic reaction, eczema, dandruff and other skin problems. Tinea pedis (commonly called athlete’s foot) is a common fungal infection that affects the foot and Tinea cruris (commonly called jock itch) is another common fungal skin infection. Eczema, also known as atopic dermatitis is dry, red, irritated and itchy skin when infected, the skin may have small, fluid-filled bumps that ooze a clear or yellowish liquid. Hives (urticaria) are red bumps or welts that appear on the body. Contact dermatitis is typically caused by exposure to an allergen or irritant. With so many ways the skin can get infected, you can imagine there is no wonder why you’re not scratching now.
Working
There are 2500 receptors on 1.2 sq. cm of your skin. One of those is the pruriceptors. These are the itch triggering receptors on your skin which release a chemical to prevent the blood from clotting when the insect bites (insect releases anti-coagulant when it bites). This triggers the immune response where our skin swells up. the nerve sends a signal to our brain for us to scratch to defend our skin from these tiny bug infestations. These nerves are the same as our pain receptors thus we instantly move into action, that is scratching. While Pain and Itch result in a different biological response from a person, “Pain generates a withdrawal response to avoid tissue damage, while itch simulates scratching to remove infestations”. This in turn releases serotonin in our brain commonly called the happiness hormone thus providing relief. Once we itch for some time, serotonin relieves us momentarily. After some time, again the cycle starts. This is scientifically called the itch-scratch-itch cycle. Itch-scratch-serotonin-relief-itch-scratch. But 1 in 5 people says scratching one place makes them itch somewhere else on their body.
Dermatographia
Dermatographia is a condition also known as skin writing. People having dermatographia lightly scratch their skin which turn into a raised wheal similar to hives. These marks typically disappear after 30 minutes. The cause of dermatographia is still unknown, but is triggered in some people by infections, emotional upset or medications such as penicillin. Most people having Dermatographia don’t seek treatment. If your signs and symptoms are especially bothersome, your doctor may recommend allergy medications such as cetirizine (Zyrtec) or diphenhydramine (Benadryl).
The signs and symptoms may occur within few minutes and usually disappear within 30 minutes. Rarely, dermatographia develops more slowly and lasts several hours to several days. To reduce discomfort and prevent the symptom: Avoid irritating your skin, don’t scratch your skin, keep your skin moisturized always.
Science through Mouse
Much of the science of itching is studied through mouse and in recent studies researchers are trying to block the gene responsible for itching, to stop scratching in extreme cases. pain and itch, as well as heat, are all transmitted by a class of nerve cells known as TRPV1-expressing neurons. When scientists use genetic engineering to create mice that don’t have these cells, the animals don’t feel any of those three sensations. The researchers bred mice that lacked the genes necessary for serotonin production. When the serotonin-free mice were injected with a substance that would normally cause itching, the researchers found that the mice did not scratch as much as a control group of mice with the serotonin-producing genes.
Next, the mice that lacked the serotonin genes were injected with serotonin. The injected serotonin caused the mice to scratch in a manner that was consistent with the control group.
The team considered different approaches that might be useful in minimizing the itching sensation. They ruled out suppressing serotonin as – although this made the mice less sensitive to itching – serotonin is too valuable a chemical in the body.
Researchers worked to isolate the receptor used by serotonin to activate these cells – called GRPR neurons. They achieved this by stimulating itching in the mice using the injected substance and then systematically activated different combinations of serotonin receptors on GRPR neurons.
Eventually, this process revealed that the receptor 5HT1A activated the itch GRPR neurons in the spinal cord. To establish that 5HT1A was the correct receptor, the team administered a compound to block this receptor in mice, which resulted in the mice scratching much less.
Treatment for itching
Applying lotion
Applying cold compresses
Using moisturizing lotions
Taking lukewarm or oatmeal baths
Using over-the-counter hydrocortisone cream or antihistamines
Avoiding scratching, wearing irritating fabrics, and exposure to high heat and humidity.
Contact your health care provider if your itching is severe, does not go away after a few weeks, or does not have an apparent cause.
You may need other treatments, such as medicines or light therapy. If you have an underlying disease that is causing the itching, treating that disease may help.
Conclusion
Itching usually prompts scratching, which can sometimes lead to a vicious itch-scratch cycle. Scratching can initially feel satisfying, but prolonged scratching just leaves you with irritated skin that can still itch and often worsens the itching itself. Since scratching provides only temporary relief and doesn't promote healing of the underlying problem, it is best to avoid scratching if at all possible. If scratching breaks open the skin, bacterial infection can set in. This is known as a secondary infection. The best way to allow irritated skin to heal is to stop scratching it. However, willpower often is not enough since the urge to scratch can be compelling.
FACT: Delusory parasitosis- This is a condition where people believe their skin is infected with flies and bugs, thus making the itching sensation a lot more compared to an average person.
“Happiness is having a scratch for every itch”- OGDEN NASH
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