This is very common practice in animals but now it is also noticed that there are certain chemicals that may enhance sexual desire in humans.
In this regard nature had made some special chemicals (insect hormones) in bees, butterflies and moths and other animals, when they are released they convey a special sexual desiring message to other bees etc.
Butterflies and moths are so sensitive in this style that they even sense these chemical about 10.6km away. Farmers had taken the advantage by keeping that weakness of bees in mind; they trap all the female bees in the trap by putting such chemical and hence preventing them from breeding in the farm.
This was the story of animals, now if I say that there are some chemicals that arouse sexual desire in men and women then it will be absolutely right.
There is a chemical known as Yohimbine an alkaloid that is found in bark of plants of genus Yohimbe, which also in use for many years for gaining power etc.
Such research is done vastly how to improve this sexual desire for opposites, but still this formula is used in perfumed only and more will be in the future.
So think a while, when girls will be attracted through chemicals not only by physical appearance etc.