Belladonna made the pupils look larger
The substance was belladonna, a preparation made from deadly nightshade. Its active chemicals, especially atropine, interfere with signals that normally make the pupil narrow. The iris—the colored ring around the pupil—relaxes, so the pupil opens wider and the eyes appear darker and more striking. The plant’s name comes from the Italian for “beautiful woman,” a reference often linked to its cosmetic use.
The effect came with a cost
A larger pupil also lets in more light, and atropine affects the eye’s ability to focus. A user could end up with blurred vision and painful sensitivity to bright light, not simply a more dramatic gaze. Because deadly nightshade is poisonous, the margin between a cosmetic effect and harmful exposure was dangerous; poisoning can affect the body beyond the eyes and can be fatal.
The beauty trick worked by disrupting normal eye function. In dim rooms, the enlarged pupils might look alluring—but outdoors, the same eyes could struggle to focus and would be unusually vulnerable to glare.
