The invention relates to a conditioning agent for reducing water absorption and dust formation of a particulate fertilizer, comprising 10 to 50 weight % of wax, 40 to 90 weight % of mineral oil and 1 to 15 weight % of a resin being mineral oil-soluble and miscible with wax and mineral oil, wherein the agent further comprises 0.1 to 1 weight % of a viscoelastic elastomer selected from the group of polyisobutylene and styrene-isoprene-styrene block copolymer which is soluble in mineral oil and has an average molecular weight of 30.000 to 5.000.000. The invention further relates to a particulate fertilizer composition, preferably a urea-ammonium sulfate (UAS) fertilizer, a urea fertilizer or a calcium nitrate fertilizer, comprising a particulate substrate, preferably an hygroscopic fertilizer, preferably a nitrogen-containing fertilizer, and 0.05 to 2 weight % of said coating thereon for reducing moisture uptake and dust formation of said fertilizer.