This formula from NAF contains simply Deet which is an extensively researched and proven fly repellent and fully HSE approved. It is not mixed with any other insect repelling ingredients as it is most effective when used alone. It's included in the formula at a level of 19.6% which NAF believe makes it the strongest available on the market whilst falling within the HSE guidelines. NAF Off Deet also comes in the option of a gel. NAF have made the concentration of Deet in the Gel weaker than in the spray as it is designed for use around the eyes and other sensitive areas. Both NAF Off Deet Spray and NAF Off Deet Gel fulfil all legal requirements and are registered as HSE recognised fly repellents (HSE No 8448 and HSE No 8447).