Of course there are reasons for some of our itches. There are the bug bites and the poison ivies and the chicken pox and the eczema, even the tickling of a hair on your face. There are also the brain tumors and diabetes and chemotherapy. (Not to make you paranoid.) But what about all those itches that just seemingly appear out of nowhere?
In a 2013 study published in the journal Science, researchers found that itching is linked to a set of neurons that produce a neuropeptide called NPPB (natriuretic polypeptide B). Although it's a step in the right process to figure out why, we can't just inhibit NPPB to stop ourselves from itching because the peptide is also released by the heart to regulate the amount of sodium released by the kidneys, which controls blood pressure (kind of important).
But realistically we probably shouldn't stop our itching anyway, as it's an evolutionary benefit that protects us from bugs and parasites. Itching can also be contagious (if I itch, you itch) and even just talking (or reading) about itching can make you itch! Feeling itchy?