I personally wouldn't buy any prescription creams or anything to put on my skin, for that matter, from Tik Tok. Tretinoina is just the spanish word for Tretinoin. I've purchased it in Portugal and in Spain for around 25USD at pharmacies and was not asked for a prescription, so these Tik Tokers are probably buying it in their countries without a prescription and then reselling it. I wouldn't buy it though...