Apart from being a nuisance, bites from insects and other arthropods can transmit a variety of diseases. When one is out of doors application of a repellent to the skin is the appropriate form of personal protection. N,N-diethyl-3-methyl benzamide (deet) is the most commonly used repellent and is generally considered more effective than any other repellent currently on the market. However, in some trials, recently developed repellents (KBR 3023, IR 3535, PMD) have shown effectiveness and persistence levels equivalent to deet. When there is a risk of encountering ticks, tucking trousers into socks and treating these with permethrin is recommended to minimise the chance of contracting tick-borne diseases. Where biting occurs indoors and at night, screening of doors and windows, use of pyrethroid treated bednets and of vaporising mats, which emit a volatile pyrethroid, are also appropriate protective measures. Buzzers and vitamin B1 are completely ineffective as insect repellents.