The majority of people are allergic to members of the toxicodendron genus, most notably poison ivy. Adverse reactions from urushiol, an oil in members of the genus, occur due to an immune response caused by its binding to skin cells, yet no rapid detection method exists to prevent exposure before it penetrates the skin. Although visual methods of identifying the toxicodendron genus and post-exposure treatments exist, there is a critical gap of time between urushiol contact and treatment. To address this issue, our biosensor was designed to produce a colored response on human skin to alert the user of contact. Escherichia coli was employed as a proof-of-concept chassis in order to ensure future safety when used in a bacteria of the human skin microbiome. Our construct uses a catechol-responsive transcription factor, the DmpR-E135K gene, paired with the lacZ gene, which produces β-galactosidase that cleaves the X-gal to generate a visible blue coloration for urushiol detection on various skin tones. This plasmid-based system integrates a chloramphenicol resistance for selection in experimentation. In the future, this biosensor could be applied in preventative dermatology through integration into topical products that provide immediate visual alerts after urushiol exposure to allow for rapid treatment.