While anyone who has been overcome by the love bug would know the symptoms well, there are underlying reasons as to why your body behaves in such a way.

Dr Jenny Wilkinson from Charles Sturt University’s (CSU) School of Biomedical Science says these strong emotions are caused by activation of the part of the nervous system that deals with responses to unexpected or stress-like situations.

For centuries, women have been leaders in mimicking such physical signs with make-up, endeavouring to make themselves more appealing to the opposite sex.

“Cosmetics mimic some of these physical signs – red lips due to increased blood flow – and hence make the person look more attractive,” she said.

“This also involves release of chemicals in the brain, including things like endorphins and dopamine, which give the feeling of pleasure.”

Dr Wilkinson said libido or sex drive is mainly due to the action of reproductive hormones such as testosterone. However, the response also depends on whether the magnetism is pure physical lust or a deeper attraction - add to this a complex mix of behavioural, physical and chemical factors.

“Some researchers have found there is a specialised area in the nose which responds to chemicals (pheromones) given off by individuals which are thought to be, among other things, sexual signals,” Dr Wilkinson said.

“There also seem to be some physical attributes that are more attractive than others – perhaps an inbuilt way of picking the best, strongest, most nurturing mate so the children have the best chance of surviving and reproducing.”

She said it is well known that in the animal kingdom, species modify mating responses due to pheromones. These chemicals are also thought to be responsible for the synchronising of menstrual cycles in women living together.

“It also seems that different chemicals are responsible for the different parts of a relationship ranging from the initial lust/attraction to the longer term emotional involvements in a more long term relationship,” Dr Wilkinson said.