The sensation of having an itch can sometimes feel unbearable. When you scratch this itch, you create abrasions that can become infected or injure your skin, thereby worsening the urge to scratch in that spot. A new study indicates that scratching particular itches can trigger inflammation and enhance your body's immune response at that specific site, which helps combat infections.
Dr Daniel Kaplan at the University of Pittsburgh stated that "scratching is often pleasurable, which suggests that, in order to have evolved, this behaviour must provide some kind of benefit". Kaplan studied his theory by breeding mice with neurons that cause the feeling of needing to itch deactivated. Known allergens for these mice were then inserted into their ears, which would normally cause the feeling of needing to itch. The reaction of these mice was compared to that of normally bred mice. Some of the normally bred mice wore cones to prevent them from being able to reach the site where they felt the itching sensation.
As expected, the results of this study showed that the normal mice scratched the itch, causing some inflammation around the site. This inflammation was explicitly triggered by the release of mast cells, which assist the immune system by facilitating the release of neutrophils. Neutrophils are white blood cells that combat infections, and their presence at this site indicates that the chances of developing an infection are reduced.
Modified mice that could not feel the itch compared to the mice that were unable to reach the itch had less inflammation in that area, which suggests that itching in those areas is the trigger to having an immune response.
To better understand this response, they applied Staphylococcus aureus, a bacteria that causes skin infections, to the area. This was done to evaluate the effectiveness of the immune response triggered by itching. After a day, the normal mice showed about ten times less bacteria on their skin compared to the modified mice and those with cones.
Although scratching has benefits in the short term, chronic itching is disadvantageous because it creates so much inflammation that the body's immune response is slowed down. So, keep your itching to a minimum.