Recently, the gamma-ray blazar TXS 0506+056 has been proposed as the source of neutrino events detected by IceCube in 2014-15 and 2017. This has further pushed the idea of blazar jets being among those cosmic sites where significant neutrino production may take place. We use a procedure based on source-internal electromagnetic cascading to constrain the environments of neutrino-producing sites in photomeson production models of jetted AGN. The role of external photon fields as the dominant target for particle-photon interactions including possible effects of the anisotropic nature of the interactions in the co-moving jet frame is discussed. We apply this procedure to the 2014-15 neutrino spectrum observed by IceCube from TXS 0506+056 to conduct a comprehensive study of these cascade spectra. By comparing these to the simultaneous multi-wavelength emission of this blazar constraints on the environment of the neutrino-emitting region are derived.