Scratching an itchy skin condition, such as eczema or a bug bite, triggers a biological feedback loop that increases inflammation and prolongs the sensation of itchiness, according to research from the University of Pittsburgh. While the action provides temporary relief, it activates mast cells that release histamine and substance P, ultimately worsening the skin’s condition.
Why does scratching make an itch feel worse?
Scratching creates a self-perpetuating cycle of inflammation. Researchers led by Daniel H. Kaplan, a professor of dermatology and immunology at the University of Pittsburgh, studied mice with allergic-contact dermatitis to understand the mechanics of this reaction. The study, published in the journal Science, found that when subjects scratched, it triggered mast cells—the body’s “alarm system”—to release inflammatory chemicals.
According to the Cleveland Clinic, these mast cells are designed to identify harmful invaders, but they can become overactive. The University of Pittsburgh study observed that mice allowed to scratch freely released more “substance P,” a signaling molecule that prompted additional mast cell activation. Conversely, mice prevented from scratching via an Elizabethan-style collar experienced less inflammation.
The urge to scratch is an evolutionary response that has existed for hundreds of millions of years. While it often feels satisfying, researchers suggest this behavior evolved as a potential defense mechanism.
Is there any biological benefit to scratching?
Despite the inflammatory downsides, scratching may serve a protective function against certain pathogens. In a follow-up experiment, the University of Pittsburgh team discovered that scratching reduced levels of Staphylococcus aureus, a bacterium commonly associated with skin infections.
Kaplan noted that these findings resolve a paradox: if scratching is damaging, why does the body reward the behavior with pleasure? The researchers concluded that while scratching helps clear bacteria, the physical damage inflicted on the skin barrier during chronic itching usually outweighs this benefit.
Pro Tips for Managing Itchiness
- Cooling relief: The American Academy of Dermatology recommends using cold compresses to soothe irritated skin.
- Medicated support: Over-the-counter 1% hydrocortisone cream may help relieve itching.
Frequently Asked Questions
- Why does scratching feel good?
- Scratching is often pleasurable, which suggests that, in order to have evolved, this behavior must provide some kind of benefit.
- What happens to the skin when you scratch?
- Scratching activates mast cells, which release histamine and substance P. This increases inflammation and can lead to a prolonged itch-scratch cycle.
- Can scratching prevent infections?
- According to the University of Pittsburgh, scratching can reduce levels of Staphylococcus aureus on the skin, though the resulting inflammation typically makes the trade-off harmful.
Have you found effective ways to manage chronic skin itching without relying on scratching? Share your experiences in the comments below or sign up for our health newsletter for more research-backed wellness tips.
