Biochemistry Of The Kiss
Life Style

Author: giulia gattino
Date: 23/01/2011


Viviamo, Lesbia mia, e amiamo
e non badiamo alle chiacchiere dei soliti vecchi troppo severi.
Il sole tramonta e poi risorge,
ma noi, una volta che il nostro breve giorno si è spento,
dobbiamo dormire una lunga notte senza fine.
Dammi mille baci, poi cento
poi altri mille, poi ancora cento
poi altri mille, poi cento ancora.
Quindi, quando saremo stanchi di contarli,
continueremo a baciarci senza pensarci,
per non spaventarci e perché nessuno,
nessuno dei tanti che ci invidiano,
possa farci del male sapendo che si può,
coi baci, essere tanto felici.

(Dammi mille baciCatullo)

Why we are so willing to kiss?


The kiss has always been representative of passions and feelings.
However, you may wonder why we are so willing to kiss.
According to a recent study by some American researchers, it is mainly a question of chemistry.
Following a test conducted among a group of students by some scholars from Lafayette College in Pennsylvania,, it resulted that, in both male and female, the very moment they kiss each other their bodies experience a thrill of bio-chemical reactions which have oxytocin and cortisol as main characters. Scientific American Mind - January 31, 2008


The bio-chemical thrill which follows the kiss, produces:

The results showed that attachment anxiety and oxytocin are positively linked in romantic attachment to a statistically significant degree, that is, the higher the oxytocin levels the higher the score on the anxiety scale of the ECR.

The authors suggest the hypothesis that this link represents one of the biological processes resulting in those rewarding emotions related to romantic attachment.

Synthesis, storage, and release

The oxytocin peptide is synthesized as an inactive precursor protein from the OXT gene.
The inactive precursor protein is progressively hydrolyzed into smaller fragments (one of which is neurophysin I, his carryer) via a series of enzymes.
The last hydrolysis which releases the active oxytocin nonapeptide is catalyzed by peptidylglycine alpha-amidating monooxygenase (PAM).

In the hypothalamus, oxytocin is made in magnocellular neurosecretory cells of the supraoptic and paraventricular nuclei and is stored in Herring bodies at the axon terminals in the posterior pituitary.
It is then released into the blood from the posterior lobe (neurohypophysis) of the pituitary gland.
In the pituitary gland, oxytocin is packaged in large, dense-core vesicles, where it is bound to neurophysin I

Secretion of oxytocin from the neurosecretory nerve endings is regulated by the electrical activity of the oxytocin cells in the hypothalamus. These cells generate action potentials that propagate down axons to the nerve endings in the pituitary; the endings contain large numbers of oxytocin-containing vesicles, which are released by exocytosis when the nerve terminals are depolarised.

  • a decrease in the levels of chortisol , a hormone depending on stress.

In particular, chortisol levels seem to drop in men the same way as they do in women; but, as far as oxytocin is concerned, the latter produces a far higher level of it in men than in women.
It is difficult to interpret these results but, according to the researchers, more than one kiss would be necessary for women to feel either emotionally or sexually involved-and, possibly, a more romantic atmosphere than the laboratory one, too.

A critical analysis of the research highlights how the given interpretation makes oxytocin a reliable indicator in both sexes of the feelings to explore, without considering the possible different bio-chemical profiles between the two sexes as it happens in other contexts.


When two lovers kiss each other, the olfactory signals and the other sensory stimuli address dopamine towards the hypothalamus –a specific brain zone- which not only checks the secretion of hormones from hypothalamus, but it also orders adrenals to produce adrenaline after the secretion of dopamine.
We have all experienced the effects of adrenaline. Blood pressure, heartbeat, sweating and saliva increase; we feel nervous and excited.


The role of saliva must not be ignored while kissing.

Prof Jhoannes Huber from Uni-Frauenklinik in Wien has pointed out that during the kiss:

  • male saliva: the male hormone of fertility, textosteron, reaches the female body through his saliva thus stimulating female libido;
  • female saliva, on the contrary, is richer in oxytocin and estrogens – i.e. female hormones which favour the emotional union with the partner.

For which sex is kissing more important, then?
According to Prof. Huber both intend it as an indicator of tenderness. However, in women the presence of female hormones in the saliva, makes the kiss more important than it may be for men because it aims to “catch” the man.

Anyway, saliva with its many protective and antimicrobial agents, Jorma Tenovuo Journal of dental research, 2002, is important not only to oral but also to general health, particularly in preventing the oral transmission of several noxious agents.


What is still to be fully understood is what triggers hormone changes: the most reliable hypothesis makes it depend on the exchange of pheromones which would result through saliva.

Pheromones are referred to as ‘ecto-hormones’ as they are chemical messengers that
are emitted into the environment from the body where they can then activate specific physiological or behavioural responses in other individuals of the same species.

Several studies indicate that humans indeed seem to use olfactory communication and are even able to produce and perceive certain pheromones; recent studies have found that pheromones may play an important role in the behavioural and reproduction biology of humans.

There is evidence of the effect of Human pheromones and sexual attraction. K. Grammer 136 et al. / European Journal of Obstetrics & Gynecology and Reproductive Biology 118 (2005) 135–142 (sense of smell in reproductive behaviours)


Helen Fisher believes that kissing produces not just a chemical, sexual thrill but can even improve overall health: “If you’re sharing your germs with somebody, you’re boosting your internal defence system.”

When you kiss, these hormones and neurotransmitters rush through your body. Along with natural endorphins, they produce the euphoria most people feel during a good kiss.

In addition the physiological effects we are sure about, of such reciprocal tenderness include:

  1. increase in blood pressure;
  2. heart rate;
  3. breath depth - Hypercapnia;
  4. eye pupil diameter;
  5. other orthosympatic function parameters.

A very interesting cognitive-emotional re-setting takes place: withdrawing of rational thinking, decreasing of prudence and self-consciousness, a reassuring effects in contrast to an apparent adrenergic and nor-adrenergic activation.

These physiological effects can be related to changes and adjustments bringing to a condition of molecular communication which, most likely, occurs at a genetic level.

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