system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How does a metal allergy work?

I have an allergy that causes a rash to form, on the skin, upon prolonged contact with metal (specifically nickel). What causes the skin to react in such a way that the skin develops a rash?
gpt
From what I've read, metal allergies are not actual allergies but actually being susceptible to irritation. With nickel for instance, one of the most common metal allergies, moisture causes salts to form that cause rashes and eczema on the skin's surface.