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Aims. We obtained Herschel/PACS imaging and spectroscopic observations of thenebula surrounding the candidate LBV HD168625. By combining these data withoptical spectra of the star, we want to constrain the abundances in the nebulaand in the star and compare them to trace back its evolution.  Methods. We use CMFGEN to determine the fundamental parameters and the CNOabundances of the central star whilst the abundances of the nebula are derivedfrom the emission lines present in the Herschel/PACS spectrum.  Result. The FIR images show a nebula composed of an elliptical ring/torus ofejecta with a ESE-WNW axis and of a second perpendicular bipolar structurecomposed of empty caps/rings. We detect equatorial shells composed of dust andionized material with different sizes when observed at different wavelengths,and bipolar caps more of less separated from the central star in H$\alpha$ andmid-IR images. This complex global structure seems to show 2 differentinclinations: 40{\deg} for the equatorial torus and 60{\deg} for the bipolarejections. From the Herschel/PACS spectrum, we determine nebular abundances of$\mathrm{N/H} = 4.1 \pm 0.8 \times~10^{-4}$ and $\mathrm{C/H} \sim1.6_{-0.35}^{+1.16} \times~10^{-4}$, as well as a mass of ionized gas of$0.17\pm 0.04$M$_{\odot}$ and a neutral hydrogen mass of about $1.0\pm0.3$M$_{\odot}$ which dominates. Analysis of the central star reveals Teff =14000K, log g = 1.74 and log (L/L$_{\odot}$) = 5.58. We derive stellarabundances of about $\mathrm{N/H} = 5.0 \pm 1.5 \times~10^{-4}$, $\mathrm{C/H}= 1.4 \pm 0.5 \times~10^{-4}$ and $\mathrm{O/H} = 3.5 \pm 1.0\times~10^{-4}$.All these measurements taken together are compatible with the evolutionarytracks of a star with an initial mass between $28$ and $33$M$_{\odot}$ and witha crit. rotational rate between 0.3 and 0.4 that has lost its material duringor just after the BSG phase.

Tracing back the evolution of the candidate LBV HD168625