In the most-watched videos, an average of 11 potentially irritating active ingredients were detected, with some containing up to 21. Among the 25 top-viewed videos, 76% contained at least one potential contact allergen, often fragrance, according to Women's Health. "The risk of allergy is most associated with fragrance," explained Dr. Tara Lagu, senior study author and adjunct professor at Northwestern Medicine's Feinberg School of Medicine. She added that many ingredients may cause sun sensitivity, noting, "Given that they're also not applying sunscreen, they could be setting themselves up for having a bad reaction to the sun."
