Heavy metal use in cosmetics poses severe health risks. In the United States, 41% of consumers aged 30 to 59 use makeup daily, while more than 90% of cosmetics contain Mercury (Hg), Lead (Pb), and Cadmium (Cd). As cosmetics are directly applied to the skin, metal ions easily enter the body through hair follicles and sweat pores, penetrating blood capillaries. Inside the body, metals bind to proteins, disrupting normal protein function, and accumulate in different organs. Therefore, the presence of heavy metals must be closely monitored, as accumulation causes serious health problems ranging from dizziness and insomnia to neurological damage and miscarriage. Current heavy metal testing often requires a laboratory setting, specialized user education, and complex detection processes. Existing metal biosensors are typically designed for environmental issues and are not adapted for cosmetics. Our project develops an all-in-one in vitro test solution that detects mercury, lead, and cadmium in cosmetics. The test incorporates genetic components, including metal-responsive transcription factors, promoters, and reporter genes. The presence of metals is indicated by a specific fluorescence within the test tube. Our product is a test that simultaneously detects three common heavy metal contaminants, enabling cosmetic manufacturers to evaluate the raw materials of their cosmetic components, and empowering consumers to test products in their homes.