Australians have used commercial creams, lotions or gels to manage our skin’s sun exposure for nearly a century.

But why we do it, the preparations themselves, and whether they work, has changed over time.

In this short history of sunscreen in Australia, we look at how we’ve slathered, slopped and spritzed our skin for sometimes surprising reasons.

At first, suncreams helped you ‘tan with ease’

Sunscreens have been available in Australia since the 30s. Chemist Milton Blake made one of the first.

He used a kerosene heater to cook batches of “sunburn vanishing cream”, scented with French perfume.

His backyard business became H.A. Milton (Hamilton) Laboratories, which still makes sunscreens today.

Hamilton’s first cream claimed you could “
Sunbathe in Comfort and TAN with ease”. According to modern standards, it would have had an SPF (or sun protection factor) of 2.

The mirage of ‘safe tanning’

A tan was considered a “modern complexion” and for most of the 20th century, you might put something on your skin to help gain one. That’s when “safe tanning” (without burning) was thought possible.

Sunburn was known to be caused by the UVB component of ultraviolet (UV) light. UVA, however, was thought not to be involved in burning; it was just thought to darken the skin pigment melanin. So, medical authorities advised that by using a sunscreen that filtered out UVB, you could “safely tan” without burning.

But that was wrong.

From the 70s, medical research suggested UVA penetrated damagingly deep into the skin, causing ageing effects such as sunspots and wrinkles. And both UVA and UVB could cause skin cancer.

Sunscreens from the 80s sought to be “broad spectrum” – they filtered both UVB and UVA.

Researchers consequently recommended sunscreens for all skin tones, including for preventing sun damage in people with dark skin.

Delaying burning … or encouraging it?

Up to the 80s, sun preparations ranged from something that claimed to delay burning, to preparations that actively encouraged it to get that desirable tan – think, baby oil or coconut oil. Sun-worshippers even raided the kitchen cabinet, slicking olive oil on their skin.

One manufacturer’s “sun lotion” might effectively filter UVB; another’s merely basted you like a roast chicken.

Since labelling laws before the 80s didn’t require manufacturers to list the ingredients, it was often hard for consumers to tell which was which.

At last, SPF arrives to guide consumers

In the 70s, two Queensland researchers, Gordon Groves and Don Robertson, developed tests for sunscreens – sometimes experimenting on students or colleagues. They printed their ranking in the newspaper, which the public could use to choose a product.

An Australian sunscreen manufacturer then asked the federal health department to regulate the industry. The company wanted standard definitions to market their products, backed up by consistent lab testing methods.

In 1986, after years of consultation with manufacturers, researchers and consumers, Australian Standard AS2604 gave a specified a testing method, based on the Queensland researchers’ work. We also had a way of expressing how well sunscreens worked – the sun protection factor or SPF.

This is the ratio of how long it takes a fair-skinned person to burn using the product compared with how long it takes to burn without it. So a cream that protects the skin sufficiently so it takes 40 minutes to burn instead of 20 minutes has an SPF of 2.

Manufacturers liked SPF because businesses that invested in clever chemistry could distinguish themselves in marketing. Consumers liked SPF because it was easy to understand – the higher the number, the better the protection.

Australians, encouraged from 1981 by the Slip! Slop! Slap! nationwide skin cancer campaign, could now “slop” on a sunscreen knowing the degree of protection it offered.

How about skin cancer?

It wasn’t until 1999 that research proved that using sunscreen prevents skin cancer. Again, we have Queensland to thank, specifically the residents of Nambour. They took part in a trial for nearly five years, carried out by a research team led by Adele Green of the Queensland Institute of Medical Research. Using sunscreen daily over that time reduced rates of squamous cell carcinoma (a common form of skin cancer) by about 60%.

Follow-up studies in 2011 and 2013 showed regular sunscreen use almost halved the rate of melanoma and slowed skin ageing. But there was no impact on rates of basal cell carcinoma, another common skin cancer.

By then, researchers had shown sunscreen stopped sunburn, and stopping sunburn would prevent at least some types of skin cancer.

What’s in sunscreen today?

An effective sunscreen uses one or more active ingredients in a cream, lotion or gel. The active ingredient either works:

• “chemically” by absorbing UV and converting it to heat. Examples include PABA (para-aminobenzoic acid) and benzyl salicylate, or

• “physically” by blocking the UV, such as zinc oxide or titanium dioxide.

Physical blockers at first had limited cosmetic appeal because they were opaque pastes. (Think cricketers with zinc smeared on their noses.)

With microfine particle technology from the 90s, sunscreen manufacturers could then use a combination of chemical absorbers and physical blockers to achieve high degrees of sun protection in a cosmetically acceptable formulation.

Where now?

Australians have embraced sunscreen, but they still don’t apply enough or reapply often enough.

Although some people are concerned sunscreen will block the skin’s ability to make vitamin D this is unlikely. That’s because even SPF50 sunscreen doesn’t filter out all UVB.

There’s also concern about the active ingredients in sunscreen getting into the environment and whether their absorption by our bodies is a problem.

Sunscreens have evolved from something that at best offered mild protection to effective, easy-to-use products that stave off the harmful effects of UV. They’ve evolved from something only people with fair skin used to a product for anyone.

Remember, slopping on sunscreen is just one part of sun protection. Don’t forget to also slip (protective clothing), slap (hat), seek (shade) and slide (sunglasses).

Laura Dawes, Research Fellow in Medico-Legal History, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

As we enter the festive season it’s a good time to think about what all those celebratory alcoholic drinks can do to your gut.

Alcohol can interfere with the time it takes for food to go through your gut (also known as the “transit time”). In particular, it can affect the muscles of the stomach and the small bowel (also known as the small intestine).

So, how and why does alcohol make your poos goes weird? Here’s what you need to know.

Diarrhoea and the ‘transit time’

Alcohol’s effect on stomach transit time depends on the alcohol concentration.

In general, alcoholic beverages such as whisky and vodka with high alcohol concentrations (above 15%) slow down the movement of food in the stomach.

Beverages with comparatively low alcohol concentrations (such as wine and beer) speed up the movement of food in the stomach.

These changes in gut transit explain why some people can get a sensation of fullness and abdominal discomfort when they drink vodka or whisky.

How long someone has been drinking a lot of alcohol can affect small bowel transit.

We know from experiments with rats that chronic use of alcohol accelerates the transit of food through the stomach and small bowel.

This shortened transit time through the small bowel also happens when humans drink a lot of alcohol, and is linked to diarrhoea.

Alcohol can also reduce the absorption of carbohydrates, proteins and fats in the duodenum (the first part of the small bowel).

Alcohol can lead to reduced absorption of xylose (a type of sugar). This means diarrhoea is more likely to occur in drinkers who also consume a lot of sugary foods such as sweets and sweetened juices.

Chronic alcohol use is also linked to:

• lactose intolerance
• overgrowth of small bowel bacteria and
• reduced absorption of fats from the pancreas not producing enough digestive enzymes.

This means chronic alcohol use may lead to diarrhoea and loose stools.

How might a night of heavy drinking affect your poos?

When rats are exposed to high doses of alcohol over a short period of time, it results in small bowel transit delay.

This suggests acute alcohol intake (such as an episode of binge drinking) is more likely to lead to constipation than diarrhoea.

This is backed up by recent research studying the effects of alcohol in 507 university students.

These students had their stools collected and analysed, and were asked to fill out a stool form questionnaire known as the Bristol Stool Chart.

The research found a heavy drinking episode was associated with harder, firm bowel motions.

In particular, those who consumed more alcohol had more Type 1 stools, which are separate hard lumps that look or feel a bit like nuts.

The researchers believed this acute alcohol intake results in small bowel transit delay; the food stayed for longer in the intestines, meaning more water was absorbed from the stool back into the body. This led to drier, harder stools.

Interestingly, the researchers also found there was more of a type of bacteria known as “Actinobacteria” in heavy drinkers than in non-drinkers.

This suggests bacteria may have a role to play in stool consistency.

But binge drinking doesn’t always lead to constipation. Binge drinking in patients with irritable bowel syndrom (IBS), for example, clearly leads to diarrhoea, nausea and abdominal pain.

What can I do about all this?

If you’re suffering from unwanted bowel motion changes after drinking, the most effective way to address this is to limit your alcohol intake.

Some alcoholic beverages may affect your bowel motions more than others. If you notice a pattern of troubling poos after drinking certain drinks, it may be sensible to cut back on those beverages.

If you tend to get diarrhoea after drinking, avoid mixing alcohol with caffeinated drinks. Caffeine is known to stimulate contractions of the colon and so could worsen diarrhoea.

If constipation after drinking is the problem, then staying hydrated is important. Drinking plenty of water before drinking alcohol (and having water in between drinks and after the party is over) can help reduce dehydration and constipation.

You should also eat before drinking alcohol, particularly protein and fibre-rich foods.

Food in the stomach can slow the absorption of alcohol and may help protect against the negative effects of alcohol on the gut lining.

Is it anything to worry about?

Changes in bowel motions after drinking are usually short term and, for the most part, resolve themselves pretty efficiently.

But if symptoms such as diarrhoea persist beyond a couple of days after stopping alcohol, it may signify other concerning issues such as an underlying gut disorder like inflammatory bowel disease.

Researchers have also linked alcohol consumption to the development of irritable bowel syndrome.

If problems persist or if there are alarming symptoms such as blood in your stool, seek medical advice from a general practitioner.

Vincent Ho, Associate Professor and clinical academic gastroenterologist, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.