It's holiday season, so many of us are partying a bit more than usual.

This means more food, more booze, more late nights and, for some, it might involve smoking the odd cigarette.

But how bad is it to smoke occasionally?

The idea that low-level smoking doesn't do you any harm is a dangerous myth, Professor David Currow of the Cancer Institute NSW said.

Social smokers often don't think of themselves as smokers, he said, so they don't believe health warnings about smoking apply to them.

But the bottom line is every cigarette exposes your body to harmful chemicals.

"There's no safe level of smoking. What's more, the negative health effects add up across your life," he said.

What type of smoker are you? Groups of low-level or occasional smokers include: The social smoker: Tends to only smoke in social settings, like at the pub or when out with friends. The binge smoker: Smokes a lot more at certain times than others, such as at the weekend. The low-level smoker: Only smokes a few cigarettes a day or just smokes occasionally. Source: Cancer Institute NSW's ICanQuit website

Simon Chapman, Emeritus Professor in the School of Public Health at the University of Sydney said: "Smoking a small number of cigarettes, say less than four a day or once a week does elevate your risk [of health problems].

"Not to the [same] extent as if you were smoking 30 cigarettes a day. But compared to someone who doesn't smoke, anyone smoking four cigarettes a day or even less is kidding themselves they're not running any extra risk."

Immediate effects

As soon as you take a drag from a cigarette, there are changes in your body, including:

You may feel more relaxed, but your blood pressure and heart rate start to rise.

You may feel more relaxed, but your blood pressure and heart rate start to rise. Your heart begins to pump differently, and the blood flow to the capillaries decreases.

Your heart begins to pump differently, and the blood flow to the capillaries decreases. Levels of a poisonous gas called carbon monoxide, increase in your bloodstream. This means less oxygen reaches the brain, muscles and other organs.

Levels of a poisonous gas called carbon monoxide, increase in your bloodstream. This means less oxygen reaches the brain, muscles and other organs. Tiny finger-like cilia which keep your airways clear of phlegm and debris are 'stunned' by chemicals in the smoke so don't do their job as well. Take a look at the comments to see what some of our readers thought about social smoking. Smoking quiz: How much do you know about cigarettes?

Less smoking, less cancer?

Even if you smoke only occasionally, you are still exposed to long-term risks.

As well as lung cancer, there are at least 13 other cancers linked with smoking.

Smoking damages DNA in cells, including in key genes that protect you against cancer.

It's true that the more you smoke, the more DNA damage or mutations you're going to create.

"But it's not your cumulative total of 40,000 mutations that guarantees you cancer. It's that you've got the right combination of mutations," Professor Curnow said.

"So you may smoke less than the person next door to you, but you might just happen to hit the genes that mean you're going to get lung cancer or any of a whole range of other cancers."

Just one to four cigarettes a day almost triples your risk of dying from lung cancer.

And social smoking is particularly bad for your heart, as bad as regular smoking, it seems.

Studies have shown light and intermittent smokers have nearly the same risk of heart disease as people who smoke daily, Professor Currow said.

Very fine blood vessels that are vital to keeping your heart healthy are damaged by smoking, he says. Harm to the same tiny blood vessels also contributes to erectile dysfunction in males.

"We know these blood vessels are vulnerable to damage at exposure to an incredibly low numbers of cigarettes," he said.

An occasional cigarette is connected to a host of other illnesses too: cataracts, reduced fertility, an increased risk of an ectopic pregnancy [where the pregnancy develops outside the uterus] and weak bones, a review of several studies showed.

Slippery slope

The direct health effects are only part of the problem with social smoking though.

Because smoking is highly addictive, smoking "a little" can all too easily turn into smoking more.

Non-daily smokers who smoke over three packs a month are just as likely to still be smoking after 14 years as daily smokers, Professor Currow said.

He notes that many social smokers binge smoke when they do smoke, rather than just having a cigarette or two.

"At present we have no way of knowing how readily a person will become addicted to nicotine until after the event, when they have become addicted," he said.

"Nicotine is one of the most addictive substances known to mankind, so experimenting in that space is not smart."

He believes the only safe strategy is not to smoke at all.

Professor Chapman agrees.

"Ninety per cent of smokers regret that they ever started. The number who say, 'Yes, I love smoking. I know the risks and I don't want to stop,' is probably less than 1 in 10," he said.

Although smoking rates have been on a downward trend, it is unclear whether the rate of social smokers in Australia is changing.

The National Drug Strategy Household Survey (2016) showed that of Australians over the age of 14, 12.2 per cent smoked daily, 1 per cent smoked weekly and another 1 per cent smoked less than weekly.

The shisha cafe trend

One form of social smoking that's a relatively recent trend is when people gather to smoke tobacco in shishas or water pipes, also known as hookah pipes.

The practice, which arose in some Arabic countries, took off in Australia several years ago, Professor Currow said.

There are now shisha cafes and hookah lounges where people smoke together, sometimes sharing the same shisha, he said.

Sometimes the smoke is flavoured by being passed through a piece of fruit like a mango or pineapple.

"People think that because the smoke is cooled or flavoured, it's harmless," he said.

"But an hour smoking socially with a shisha is equivalent to 50 or 100 cigarettes. You can get very major exposure over a short space of time."

Kicking the habit

The good news is that as soon as we stop smoking, your body starts recovering.

Within 12 hours of your last cigarette, blood carbon monoxide levels are much lower and after a year, the risk of coronary heart disease will be half of what it once was as a smoker.

If you quit before the age of 35, your life expectancy will be much the same as someone who has never smoked.

If you're a social smoker wanting to quit, it can help to ask friends to discourage you from smoking in social situations.

Cutting down on alcohol can also help some social smokers who tend to smoke more when they drink.

And you might think about the people around you who have to breathe in the smoke you exhale in social situations. Some research has suggested this is a stronger motivator for social smokers to quit than education about health impacts on yourself.

"Social smokers say, 'I'm not addicted'. If that's really the case, walk away from it," Professor Currow said.

If you find you have trouble walking away from it, help is available.

You can find resources to help you quit on the Australian Government's Quitnow website.

Additional research by Claire Pain.