[Testing of industrial repellents against gnats and horseflies]. 
According to the Austrian Cosmetic Recommendation a minimum period of protection of 2 hours is to be provided.  This applies to the preparation on the market with the substance "Merck 3535" in aqueous concentration in the tested area.  However, this protection period was not achieved for horseflies.  In test trials the characteristic of the individual nuisance should be taken into account.