In 2018, a 19-year-old French student named Estelle suffered a severe allergic reaction after using a home hair dye kit containing para-phenylenediamine (PPD), a common chemical in many permanent dyes. Although she did a patch test, she waited only 30 minutes instead of the recommended 48 hours before applying the product. Soon after, her scalp began to itch and swell, and by the next day, her head had ballooned dramatically, her skull’s circumference increased from about 22 inches to nearly 25 inches. She also experienced tongue swelling and trouble breathing, prompting an emergency hospital visit where she received treatment including an adrenaline shot. Estelle eventually recovered and later spoke out to raise awareness about the importance of following patch test guidelines and recognizing the risks of allergic reactions to hair dye ingredients like PPD.