It depends on the case; there is no single guideline.
Effect by goal · level of evidence
Possible carcinogenicity (product safety)
no clear effectLowstudy (A)
Review of the debate: in the 1970s several aromatic amines in dyes were carcinogenic in rodents and were banned in the EU; current p-phenylenediamine shows weak genotoxicity in vitro. Evidence of real risk in people remains debated.
Possible carcinogenicity (product safety) — no clear effect (Low, study). Review of the debate: in the 1970s several aromatic amines in dyes were carcinogenic in rodents and were banned in the EU; current p-phenylenediamine shows weak genotoxicity in vitro. Evidence of real risk in people remains debated. 17661215
Information, not medical advice. Prescription drugs require a doctor.
Information, not medical advice. Scientific evidence reflects the quality of the studies.