Like trying to reach a mosquito bite on your upper back, scientists have been struggling to get at an answer to why we itch — and why it feels so good to scratch an itch — ever since it was proven that itching is a separate sensation than pain.

Like pain, itching involves a system of nerves, molecules and cellular receptors that allow communication between the skin and the brain. While there’s some overlap between the circuits that communicate both pain and itchiness, there are enough unique pathways to distinguish itch as its own condition.

New research also shows that scratching an itch activates numerous areas in the brain beyond mere sensation: areas involved in pleasure, reward, addiction, craving and motivation. This could help explain why scratching an itch also feels so good … and why scratching is prevalent among most species of the animal kingdom.

This finding could also lead to new treatments for itching disorders, such as chronic itching. Chronic itching has no direct cause; it’s not a result of poison ivy or a furry sweater, and thus can’t be relieved with a quick scratch or an antihistamine. Instead, it can result from a range of issues, from skin conditions to drug side effects, nerve disorders or internal diseases. While chronic itching affects about 10 percent of the population at some point in their lives, it’s more common in older adults, possibly due to deteriorating nerves in the skin that activate itch receptors without cause.

Now that researchers have a better understanding of chronic itch, the race is on to create pharmaceuticals that can actually soothe the savage sensation. One day soon, medication may be available that blocks certain cell types or directly targets itch receptors. But for now, relief remains just out of reach.