What is the origin of the idiom "get under one's skin" and when to use it?

The exact origin of the phrase "get under one's skin" is uncertain but it likely emerged from the idea of something or someone causing a strong emotional reaction that feels deeply personal and invasive. The phrase draws on the physical sensation of irritation when something is touching or bothering the sensitive layer beneath the skin. This idiom is often used in interpersonal relationships, such as when someone's actions or words consistently provoke frustration or anger. It can also be used to describe situations where external factors, such as a challenging task, a difficult situation, or an ongoing problem, have a profound impact on someone's emotions or mental state.