Is this product also suitable for use in a regular shower or with a facial steamer?

Using it in a regular shower is not recommended. The product is intended for dispersion in a larger volume of steam, as found in a sauna, steam room, or a full bathtub. In a confined shower cubicle, the concentration of aromatic compounds in the air could become very high very quickly, potentially causing discomfort, overwhelming scent, or irritation to the eyes and respiratory tract. The smaller space and lack of controlled dispersion make it unsuitable.

It should not be used with facial steamers or any device designed for direct inhalation. These devices concentrate steam very close to the face and airways. Introducing a cosmetic product not specifically formulated for this purpose risks exposing delicate mucous membranes and skin to undiluted components, which can be irritating or cause adverse reactions. For facial steamers, only use products specifically designed and labeled for that intimate, direct-inhalation purpose.