At present, Brackenfern is classified as carcinogenic 2B. Epidemiological evidence may be related to the high incidence of bladder cancer in some areas, and animal experimental evidence is that it can cause bladder and upper digestive tract cancer in rats.

Ptaquiloside is the main carcinogen in ferns, which can alkylate adenine and guanine in DNA.

Students who say that "talking about the effect without talking about the dose is hooliganism" should pay attention. Protopterin is a genotoxic carcinogen, and its toxic effect has no threshold, that is, there is no safety limit. We can calculate an actual safe dose, but even at this dose, the possibility of cancer is still not zero. Of course, protopterin also has a dose-response relationship, that is, with the increase of dose or frequent contact, the possibility of cancer increases, but it is really not.