An insect repellent composition comprising p-menthane-3,8-diol, vanillin, an antioxidant that prevents discolouration of said vanillin when said composition is stored at 54 °C for 14 days and a delivery vehicle is provided. The delivery vehicle is preferably water and at least one alcohol, preferably isopropyl alcohol. The antioxidant is preferably sodium bisulphite. An insect repellent composition comprising p-menthane-3,8-diol (PMD, Oil of Lemon Eucalyptus) as the sole insect repellent, vanillin and a delivery vehicle is outlined. Insect repellent compositions comprising PMD, vanillin and a delivery vehicle are provided that are suitable for once or bi-daily administration, useful for the prevention of the Zika virus, for repelling the Scottish Highland midge and for the prevention of a disease state caused by the Culex mosquito. The compositions may be formulated as a spray, lotion, gel or roll-on. A container containing a formulated composition is provided. An article of manufacture, such as a mosquito net or dermal wipe impregnated with the compositions is provided. A method of preventing a disease state cause by a biting fly, or repelling a biting fly by application of the insect repellent composition to the skin of a user is described.
