What causes pimples, why do teenagers get them, and should I pop them?

Australians tend to call them pimples, North Americans say “zits”, while in Scotland, they’re dubbed “pleuks”.

Whatever nickname you use, these little lumps on the skin, known by doctors as “acne vulgaris”, are a fact of life for most of us, especially when we’re teenagers.

There are some wild theories out there about why humans evolved to get pimples in the first place.

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One idea is the oily substance that causes zits helps babies slide out more easily at birth.

Another is that spots make adolescents less desirable to potential mates — at least until they grow up more and can handle becoming a parent.

Imaginative hypotheses aside though, what do we really know about pimples and what triggers them? And, most importantly: should we pop them or not?

Where do pimples come from?

A pimple is basically a hair follicle that gets clogged with bacteria, dead cells and a fatty liquid called sebum produced by a gland connected to the pore.

The bacterium that contributes to acne, known as Cutibacterium acnes (formerly known as Propionibacterium acnes), is a natural inhabitant of our hair follicles. 

In some pimples, like the classic pus-filled ones, the bacteria multiply when they feed on excess sebum.

“The metabolites produced by that digestion are inflammatory,” University of Melbourne dermatologist Rod Sinclair says.

The body’s immune system kicks in. White blood cells are sent to the follicle where they engulf and digest bacteria, then die. As dead white blood cells accumulate, they form a yellowish head, Professor Sinclair explains.

Professor Sinclair calls these inflammatory pimples “yellowheads” or pustules. They’re just one item on a whole menu of pimples, some of which do not involve inflammation, such as blackheads.

Blackheads are much-misunderstood. They are often seen as a sign of dirty skin, but their dark colour is simply discolouration of the core of the pimple, which is open to the air and turns black when exposed to oxygen.

“So when you squeeze a blackhead, the first millimetre is black and the rest of it is cream-coloured,” Professor Sinclair says.

Why is acne such a teen thing?

The most common trigger for acne is puberty, thanks to the teenage flush of sex hormones called androgens.

Almost every teenager around the globe gets some level of acne, Professor Sinclair says.

“I don’t think that there is any ethnic group on the planet that’s spared from adolescent acne vulgaris.”

Androgens are produced by males and females, and they stimulate production of the sebum that is central to pimple formation.

While acne usually goes away by our 30s, some people are affected well into their 40s and 50s.

Hormonal changes triggered by menstruation, pregnancy, or hormone-containing medications can also cause acne. And there is evidence stress can make it worse by activating the immune system.

On top of this, some diseases can cause acne. It’s a side effect of polycystic ovary syndrome, for example.

So if you are an adult and get acne for the first time, it’s wise to see the doctor.

Can you inherit acne or is it environmental?

A slew of genes have been linked to acne, and there is evidence ethnic groups with darker skin are more likely to have acne than others.

But, Professor Sinclair says, whether or not you can inherit it is not straightforward.

“There are so many factors that affect its susceptibility … so it’s not going to run through in families in in any way that’s predictable.”

And if you feel like you get more pimples when it’s hot, there may be some evidence to support this, but Professor Sinclair warns people can mistake heat rash for pimples.

What can increase the risk of acne is air pollution, well as greasy cosmetics, so aim for those labelled “non-comedogenic”. They are not supposed to block your pores.

But when it comes to acne apparently caused by wearing masks — dubbed “maskne” — Professor Sinclair says most of this has not been true acne, but another condition called rosacea.

Does eating chocolate really make acne worse?

You may have heard about the role of different foods in aggravating acne.

But the scientific evidence is often scant or not clear cut.

For example, while chocolate has been a suspected trigger for acne for decades, there is no consensus it is a culprit.

Studies suggesting that avoiding milk or having a diet of low-GI foods (those that have little effect on your blood sugar levels) could reduce the risk of acne are also inconclusive at this stage.

“There is no meaningful data that food makes an impact, and that modification of your diet can meaningfully treat your acne,” Professor Sinclair says.

Having said that, though, he accepts people might beg to differ.

“If a patient says to me, ‘Every time I eat chocolate or I have fried chicken, I get pimples’, I say … ‘If there is a food that you’ve found causes [acne] directly, then it makes sense to avoid it.’

“But if you haven’t identified any food that causes acne, then there’s no allergy testing or food testing that we can do to identify that food. And it’s unlikely that it’s really important in your acne.”

What treatments work?

Of the stack of products out there that claim to give you pimple-free skin, Professor Sinclair says only some consistently deliver on their promise.

For mild cases of those pesky pustules, he recommends topical products containing benzoyl peroxide. The chemical has been around for half a century and can be bought without a prescription at the pharmacy.

It’s an antiseptic that kills microbes on the skin, including C. acnes.

But it’s a relative of bleach, so take care when using it around coloured towels and clothes.

And depending on your skin sensitivity, you might benefit best from a product in the form of a gel, cream or wash, Professor Sinclair adds.

Unfortunately getting rid of blackheads or serious cases of acne is more complicated, and may require prescription medicine.

For inflammatory acne, doctors tend to prescribe the drug isotretinoin (for example, Roaccutane), which reduces the amount of sebum made in your skin pores.

But while isotretinoin can reduce scarring, some people suffer side effects from this medication, including headaches and skin flare-ups.

And a recent study has underscored warnings that women should be on contraception when using the drug because it has been linked to serious birth abnormalities.

If you are unable to take isotretinoin, or are concerned about its side effects, a long-term course of antibiotics may be prescribed instead.

Should we pop our zits?

Left alone, pimples will generally pop and heal themselves, but that doesn’t stop us trying to hurry them along.

Research suggests humans are so drawn to popping pimples that even just watching others do it activates the pleasure centre of the brain.

Satisfying as it might be to “pop a pleuk”, doing so can make matters worse.

It can let not-so-friendly bacteria in, aggravate inflammation, and make it harder for the pimples to heal without leaving marks on your face.

Still, says Professor Sinclair, it’s “wishful thinking” to think people won’t give it a try, which is why there’s quite a bit advice out there on how to pop zits safely.

So if you must do it, here’s Professor Sinclair’s advice.

“If you have a fully ripe pimple ready to pop, it is okay to squeeze it as long as you stop at the first sight of blood.

“And then cover the pimple with micropore [wound dressing] tape so you’re not tempted to pick at the crust that forms after.”

Professor Sinclair says if you keep picking and squeezing after you draw blood, you can do damage that delays healing and could lead to scarring.

“In other words,” he says, “it’s important to know when to stop.”

Listen to Dr Norman Swan and Tegan Taylor discuss the who, why and what (to do) about acne on What’s That Rash? And subscribe to the podcast for more.