Does a quack only refer to doctors?

No, the term "quack" does not only refer to doctors; it can apply to anyone who pretends to have expertise or knowledge in a particular field but lacks the necessary qualifications or credibility. This includes individuals promoting fraudulent or unproven treatments, products, or services in various areas, such as health, finance, or wellness. Essentially, a quack is someone who deceives others by offering false claims or misleading information.