You know you better stay off it, and yet you do it: scratching a itchy scab
. Only: you often scratch the wound open and a new itchy scab develops. A recipe for an endless cycle. Why do those scabs itch and why is that scratching so satisfying? And is it necessarily bad?
Koen Quint, dermatologist at the Leiden University Medical Center, first gives a basic wound healing course. “Whether or not a scab develops depends on the nature and depth of the wound,” he says. A healing cut usually contains some clotted blood, but the maddening scab grows mainly on superficial wounds, such as scrapes. Gradually, the edges of such a scab loosen a bit: great to put on your nail. The scab will remain on your skin like a mushroom for a while, getting smaller and thinner on a stalk, until it falls off. Spontaneously or not.
Scabs consist of the dried remains of a blood clot: a tangle of fibrin threads in which platelets get stuck, to stop the bleeding. “That hard crust serves as a temporary replacement for your normal skin,” explains Quint, “so that you remain protected against external influences, such as infections. The scab also protects the fragile new skin underneath.”
Initially, a wound mainly hurts because sensory nerves in and under the skin are damaged. But as soon as the skin under the scab starts to heal, sometimes itching occurs. “Various explanations have been suggested for this,” explains Quint, “such as a lack of fluid around the wound, or the migration of new epithelial cells under the scab. In addition, the wound produces substances that can stimulate itching nerves.”
Why? Does the body regulate that itch on purpose, because scratching stimulates circulation? “No”, answers Quint. “The substances that cause itching are probably necessary for the wound to heal properly, the itching itself is an annoying side effect.”
And why does scratching make you feel good? Quint: “The theory behind it is that scratching activates the pain nerves. The brain registers this pain, after which it starts to release serotonin: a substance that can give a feeling of relief.”
Just as there are people who have an uncontrollable urge to pull out hair or eyelashes (a condition known as trichillomania), you also have people who systematically scratch away all skin imperfections, such as scabs or pimples – even if they are not itchy or barely noticeable. To Be Visible. Experts speak of dermatillomania, a form of self-harm that falls under the obsessive-compulsive disorder.
“It gives me a nice, calming feeling when I’ve managed to scrape a scab off a wound,” writes Caro Suringar in her blog about the phenomenon. “At the same time, it also makes me feel guilty afterwards: why can’t I stay off it?” This blog writer often picks when she’s tense – or, on the contrary, when she’s bored. She sees it as a form of dysfunctional emotion regulation: she literally tries to scratch away the tension or boredom, instead of acknowledging it and doing something about it.
All in all, we’d better stay away from those scabs. “If the scab is not really loose on the skin and the skin underneath has not yet healed properly, you can also take the healing skin with you by removing the scab,” says dermatologist Quint. “The healing process then starts all over again. In fact, with a deep wound it can lead to scarring.”
Masking helps to reduce the urge to scratch.
A version of this article also appeared in NRC Handelsblad of 25 September 2021
A version of this article also appeared in NRC on the morning of September 25, 2021