I bought milk powder in a maternal and infant shop and said someone sold it to me. Can I sue?

Of course. When buying milk powder in a maternal and infant store, if the merchant claims that it was sold to you by an individual, but it is actually a commercial act, he has the right to take legal action. As a consumer, he has the right to enjoy the protection of legitimate rights and interests, including buying genuine products and obtaining real commodity information. If the merchant intentionally conceals the identity of the merchant, he can claim his own rights and interests. If a merchant intentionally provides false information or engages in fraudulent acts, such as false propaganda and selling fake and inferior products, he can bring a lawsuit against his fraudulent acts.