What is this ?

Jè ✨ • 20 Somethin` 🤫🤞🏾. Twin Muva 👑 + 1 Xya Raine due January 7th 2019 💙. Business owner and up and coming YouTuber 😘💅🏾

My 8mo old daughter has this around her neck and belly button. Her twin brother does not. They get baths every night in baby dove. Of course very active and crawling, into everything during the day. Anybody know what this is ?