From Latin: repellere = to push back.
This term describes the activity of chemical products – obtained from plants by isolation process or by synthetic chemical reactions – against blood sucking arthropods. These products cover the “natural smell” of human and/or animal skin, so that insects, ticks, mites etc. do not recognize their potential hosts and stay away. This protection period is in general rather short and lasts mostly only a few hours in case that true insecticides (such as imidacloprid, permethrin, e.g., in repellents used for dogs) are not included in the repellent products. When using plant extracts (e.g., essential oils) – even in higher concentrations of 20 % and above – the protection period is very short (less than 1 h). Furthermore, many essential oils have an enormous allergenic potential, so that they threaten the health of users – especially that of children.
The history of the development of chemical repellents is enclosed in the key word Saltidin.