According to Paula's Choice:
"ylang ylang
Rating: POOR
Categories: Plant Extracts, Antioxidants, Fragrance: Synthetic and Fragrant Plant Extracts, Sensitizing
Fragrant, volatile oil that can also be a skin sensitizer, though it's also a potent antioxidant and may help improve uneven skin tone. It presents a bigger risk when used DAILY rather than intermittently."