Cow manure/dung has a special place in vedic hindu tradition. Cakes made from cow manure/dung & herbs are ideal for fire sacrifices (yajnas) and for various ceremonial rituals. The smoke of cow dung clears the air of germs creating a pure and holy atmosphere.
They also act as an excellent insect & mosquito repellent & are much better than the chemical based mosquito repellents that emit poisonous & harmful fumes causing health related problems.