3 November 2018 | NewScientist | 13Alice KleinBROWN spots on skin caused by
long-term sun exposure can be
removed using medicated creams,
a process that may help prevent
some skin cancer.
While the skin pigment
melanin can help screen us from
some of the effects of the sun’s
ultraviolet rays (see page 18),
long-term exposure can still lead
to brown or pink scaly marks on
the skin, called actinic keratoses.
Also known as sun spots, these
can go on to become cancerous.
In the past, sun spot removal was
usually done by freezing them
with liquid nitrogen, but the
pain this caused meant that only
one or two spots could be treated
at a time.
Creams that remove dozens of
sun spots at once are a less painful
alternative. Now a study led by
Janne Räsänen at the University
of Tampere in Finland has
highlighted the most effective –a cream based on aminolevulinic
acid (British Journal of
Dermatology, doi.org/cwc3).
After aminolevulinic acid is
applied to the skin, it is absorbed
by sun spots and forms a chemical
called protoporphyrin IX. People
must keep the cream on for2 hours while sitting in sunlight,
which triggers protoporphyrin IX
to release molecules called
reactive oxygen species. These
cause the cells in sun spots to die
and ultimately fall off.
The prescription cream is
normally applied once and works
quickly, says Stephen Shumack
at the University of Sydney.
It does inflame the skin though.
“You look like you’ve had a bad
sunburn for the first few days,
then the skin gets scabby andcrusted over and the sun spots
peel off within a week,” he says.
“The skin looks a lot better
afterwards – it becomes very
smooth,” says Shumack.
Räsänen’s study, which took
place in Finland, compared the
effectiveness of two different
creams when used by 69 adults.
They were aged 49 to 92 and had
an average of 11 sun spots each,
although some had as many as 32.
The cream with aminolevulinic
acid was more effective, removing
80 per cent of a person’s actinic
keratoses. The majority of the
participants said using this
cream was almost completely
painless. The other cream the
study looked at contained methyl
aminolevulinate instead, and the
team found it removed 74 per cent
of the keratoses.
In Australia, aminolevulinic
acid does not fall under the
government’s drug subsidy
scheme, so many people use less
expensive fluorouracil cream
instead. This is also effective for
removing sun spots over large
areas, but must be used daily for
about four weeks and causes more
irritation, says Shumack.
Rob Brazier, a retired farmer
in the rural town of Jandowae
in Australia, recently tried
fluorouracil cream to treat the
spots on his arms, face, ears and
chest. “It’s a bit scary at first
because you get all these raised
sores where the cream is reacting
and the itchiness drives you
crazy,” he says.
After a few weeks, Brazier’s sun
spots started to scrape off when
he washed. Five months later,
he is pleased with the results.
“My skin looks pretty good now.”
In farming areas like Brazier’s,
where high sun exposure has
been a way of life, the use of such
creams seems to be catching on.
“Everyone you speak to knows
someone who’s doing it. A lot of
people here grew up the same way
I did – you’d work out in the sun
ploughing all day with no shirt
on and often no hat, and you
wouldn’t think anything of it.” ■MANY small mammals huddle
together to keep warm in winter.
It now turns out that this behaviour
also changes the composition of
bacteria in the animals’ guts in a way
that seems to slow their metabolism
and help them conserve energy.
To investigate the effect of
huddling on the microbiome, Dehua
Wang at the Chinese Academy of
Sciences in Beijing and his colleagues
put voles in a room at 4°C. They placed
some in a single cage so they could
huddle together for warmth, while
others were kept alone.
After three weeks in these
conditions, Wang and his colleagues
extracted gut bacteria from both sets
of voles. They used antibiotics to
sterilise the guts of another 12 voles
kept at 23°C, and then seeded six
of them with “huddling” vole gut
bacteria and the other six with
“isolated” vole bacteria.
They found those with huddling
vole bacteria in their guts consumed
15 per cent less food and had a resting
metabolic rate 20 per cent lower than
those with bacteria in their guts from
the isolated voles.
The finding suggests that huddling
in the cold triggers changes to the
gut flora that slow down the voles’
metabolism. This might be useful
given that food is often scarce in
winter (Microbiome, doi.org/gdqk5m).
Wang’s team found a greater
variety of bacteria in the huddling vole
microbiome. They also noticed a spike
in the concentration of one particular
group of bacteria, Lachnospiraceae.
These can generate short-chain fatty
acids by breaking down dietary fibre.
Wang says these fatty acids can
be absorbed into the body of the
host animal, which could explain why
voles with lots of these bacteria in
their gut don’t need to eat as much
food as normal.
“This is the first time we have
shown that huddling behaviour
changes animals’ gut bacteria,”
Wang says. Yvaine Ye ■
DAVID TROOD/GETTYFor daily news stories, visit newscientist.com/news“ It’s a bit scary at first as
you get all these raised
sores, and the itchiness
drives you crazy”Huddling makes
vole gut more
energy efficient
Rubbing off years
of sun exposure
NEWS & TECHNOLOGY