A Natural oils composition for hardening and strengthening fingernails and toenails in which the natural oils contained therein exhibit ability to self polymerize into a solid film in the presence of oxygen. Oils of this invention are diluted with compatible solvents allowing penetration into the nail. Oils of this invention exhibit an Iodine Value greater than 140 grams of iodine absorbed per 100 grams of oil as measured under the prescribed conditions of a standard method described forthwith. Fingernail strengthening and conditioning compositions with antifungal properties are also disclosed.