Repellent

Repellents (from the Latin repellere-vertreiben), also known as insect repellents, are a group of substances which, in various forms, can be used to combat insects. They are a group of substances which, incorporated in various bases (spray, aerosol, cream, lotion, oil), serve to deter insects (especially mosquitoes), spiders and mites. After application to the skin, the repelent evaporates slowly, developing an odour coat that repels the insects.

Sebum is considered a natural repellent (sweat is said to have the opposite effect).

Essential oils belonging to the monoterpenes (e.g. eucalyptus oil, cedar oil, citronellol) and other natural products, e.g. camphor oil, also have a certain repellent effect.

Repellents are evaluated according to their effectiveness, their duration of action and their possible toxic or allergic potency. They are applied directly to the exposed skin areas. They can also be used to impregnate clothing or mosquito nets.

Unclear, but the influence on the insects' sense of smell seems to be a significant factor. In principle, a repellent must evaporate and is all the more effective the more volatile it is, although this property reduces the duration of action. For modern repellents a reliable duration of action of at least 6 hours after application is stated.

Examples of repellents:

Chemical repellents

• Icaridin (Bayrepel®, Autan®)
• Dibutyl phthalate
• Dimethyl phthalate
• DEET (N,N-diethyl-3-methylbenzamide 2-ethyl-1,3-hexanediol and 3-(N-n-butyl-N-acetyl)-aminopropionic acid ethyl ester)
• EBAAP (ethyl butyl acetyl aminopropionate)

Herbal repellents

• Essential oils from various Representatives of the labiates such as: basil, mint, lavender, sage, thyme.
• Essential oils from myrtle plants: eucalyptus, cloves, tea tree. The best herbal repellent is citridiol, an essential oil extracted from a type of eucalyptus.
• Essential oils of aromatic sweet grasses - citronella, lemongrass, plamarosa - (see citronellol below)

A mosquito repellent WHO recommendation for the tropics refers to bed nets. These should be impregnated with a "long-acting low volatile pyrethroid such as: deltamethrin, alpha-cypermethrin, permethrin, etofenprox. Such "long lasting insectidial mosquito nets" ILIN`s are used in Africa for mosquito prophylaxis. Clothing prepared in this way can also be used as tick protection.

The combination of sun protection and insect screen is a rather problematic alliance. Therefore, it is recommended to prepare the clothes with repellents and to apply the sun protection filter directly on the skin.

1. Hofmann H (2015) Repellants. In: Ev.Stebut (Ed.) Travel medicine. Springer Publishing House Berlin-Heidelberg294-297
2. Care F (2009) Prevention with repellent in children. Arch Pediatr 16 Suppl 2: S115-122.
3. Uzzan B et al (2009) Efficacy of four insect repellents against mosquito bites: a double-blind randomized placebo-controlled field study in Senegal. Fundam Clin Pharmacol 23: 589-594.