Biocides are substances which are used to fight off living organisms. Their effect is to disturb essential functions or kill undesirable or harmful microorganisms, insects or plants.

There are chemical biocides like chlorine, the most frequently used bactericide, as well as biotechnological produced substances. Biotechnological biocides are mostly secondary metabolites of microorganisms which in their functionality compete for the nutrient supply and therefore leave the undesirable microorganisms without nutrition in order to prevent them from growing and spreading. Bactericides (effective against bacteria) or fungicides which work against fungi are some examples.

Since the EU-guideline 98/8/EG came into effect in 14^th January 1998 all new biocides are subject to approval of their effect on all relevant protective goods. Important aspects are human health, as well as effects on pets, farm animals and also environmental aspects.