A heady mix of infatuation and attraction, the unmistakable flutter in your stomach and the realisation you are in love.
Your appetite wanes as you anxiously look forward to seeing the object of your affections, and your mind wanders, their presence occupying your every thought.
But a surge in your libido and a rise in testosterone levels in the body can leave you more prone to suffering an outbreak of unsightly spots, scientists say.
A new psychological study of couples identified the five stages of love - butterflies, building, assimilation, honesty and stability.
A new study by dating website eHarmony has identified the five stages of love - butterflies, building, assimilation, honesty and stability
Those taking part were asked to complete a psychological test to determine their true feelings.
The findings, collated by dating website eHarmony, were grouped into five stages.
Participants were asked questions about their behaviour and lifestyle, in order to uncover the impact love has on a person's health at each stage.
Psychologist Dr Linda Papadopoulos, who assisted with the study, told MailOnline the aim was to establish if there are distinct stages of love, how people feel and what happens to them physiologically.
She said: 'It's fascinating to note that this one core emotion can be broken down into such distinct stages.
'What's more, each stage may be relived and recaptured as couples grow into a relationship, and face different life challenges together.'
Psychologist Dr Linda Papadopoulous said the different stages of love impact on our health, causing weight loss, a lack of sleep and raised stress levels
STAGE ONE: BUTTERFLIES
And the findings suggest of the 33 million Britons currently in a relationship, two per cent - or 588,000 people - were found to be enjoying stage one.
Marked by intense infatuation and sexual attraction, symptoms noted by couples included weight loss (30 per cent) and a lack of productivity (39 per cent).
Biologically, it's reported that during this early stage of dating, both men and women create more of the sex hormones testosterone and oestrogen.
As a result more than half - 56 per cent - noted an increase in their libido.
Dr Papadopoulos told MailOnline: 'First comes butterflies - we have all felt it, it's visceral - you just feel it.
'Butterflies is a great way to describe it, the time when you can't stop having sex.
'We found people almost forget to eat, there is a sense people are full on love.
'Productivity is not great at this stage, as people's minds constantly wander.
'And interestingly, people tend to get pimples in the early stages of a relationship.
'This is because increases in testosterone cause a rise in sebum, which can block pores and cause a breakout.'
STAGE TWO: BUILDING
As the initial attraction gives way to learning more about one another, the honeymoon stage subsides and a couple begin to build their relationship.
eHarmony's study estimated around three per cent of Britons in relationship are currently at stage two.
The body releases neurochemicals called monoamines, which speed up heart rate, trigger rushes of intense pleasure and replicate the effects of Class A drugs.
The biological effect culminates in a feeling of 'happy anxiety', where people can think of little else than their blossoming relationship.
Forty-four per cent of the study participants noted a lack of sleep while 29 per cent reported a their attention span had been adversely affected.
'Love changes, it moves slightly further to the point where you are building your relationship, getting you know your partner,' Dr Papadopoulos said.
'You may find your attention span is really awful, and you're not able to focus.
'It can also be difficult sleeping, you're literally kept awake thinking about the other person. And there is a sense of happy anxiety, where you feel drunk on love.'
STAGE THREE: ASSIMILATION
Having established whether the other person is 'right', stage three forces a couple to question whether the 'relationship' itself is right.
Questions over the future of the union and forming boundaries in the relationship can lead to a rise in stress levels, reported by 27 per cent of those taking part in the study.
Stage one increases libido, while stage two releases chemicals that replicate the effects of Class A drugs. Love can also impact weight loss, stress levels and sleep patterns
Dr Papadopolous said: 'The third stage is when it becomes more serious, you start thinking "this is more serious than I thought", and "I know you but where are you at in your life, do we want the same things", and "can we figure this out".
'You begin to see that you assimilate that person into your life.'
STAGE FOUR: HONESTY
She said this combined with stage four, where people open up showing the 'real you' sees the first real rise in stress levels and anxiety.
'This stage deals with the concept behind how we all put on our best faces, through social media we edit our lives as well as our pictures to make it appear as though everything is fine,' she said.
Opening up completely triggered feelings of doubt and increased vulnerability in 15 per cent of participants.
Dr Papadopolous said: 'Interestingly stages three and four see an increase in stress levels.
'Up until now it has been wonderful, feelings of happiness and being content.
'But the more serious the relationship becomes, the more people worry, "is it what I think it is"?'
'Vulnerability and stress can manifest itself in various ways, causing unease and obsessiveness around the relationship.'
STAGE FIVE: STABILITY
But if a couple can weather the emotional rollercoaster of the first four stages, the fifth and final stage, stability, brings with it increased levels of trust and intimacy.
eHarmony found 50 per cent of respondents had reached this stage, and 23 per cent reported feeling happier as a result.
Biologically, vasopressin - a powerful hormone released by men and women during orgasm - strengthens feelings of attachment.
The fifth stage, stability, brings with it increased levels of trust and intimacy after weathering the emotional rollercoaster of a relationship
Meanwhile oxytocin - released during childbirth - deepens feelings of attachment.
'This is where we see a real level of contentness,' Dr Papadopolous told MailOnline.
'We found the body releases wonderful hormones which helps couples bond. We noted a real sense of attachment, and a sense of "you have got my back and I've got yours".
Jemima Wade, spokesperson for eHarmony.co.uk, said: 'Here at eHarmony, we're responsible for tens of thousands of relationships and millions of "butterfly" moments every year as a result of getting to know both the heads and hearts of our members.'
'While love doesn't have a rule book, our unique compatibility system matches members on the 29 key personality dimensions needed for a successful relationship including emotional temperament, core values and social skills – giving singles the best possible matches and better dates.'
Read more: http://www.dailymail.co.uk/health/article-2812818/Why-falling-love-gives-spots-makes-feel-like-drugs-Scientists-reveal-five-stages-relationship-affect-health.html#ixzz3Hdr4QwDg
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