Bruises are painful, none-too-memorable
souvenirs left from fresh misfortunes, which
manifest in a range of colours that transform
over time. They begin from the ‘freshly minted
red’ to the ‘unnaturally rich purple’, and finally
to the ‘healing jaundice yellow’. Most commonly
arising in response to blunt force that traumatises
the skin’s underlying tissues and blood vessels,
bruises form beneath the skin’s surface due to
blood leakage from damaged vessels that settles
into the surrounding interstitial fluid. Investigating
the changing colours of bruises has the potential
to reveal information on the nature of the incident
and the age of the bruise.
What gives rise to the tentative colours of
bruises is primarily haemoglobin, a dominant
chromophore that plays a role in determining the
colour of our skin. The initial red colour is given off
by haemoglobin itself. The body then produces an
inflammatory reaction in response to the spillage,
to remove blood from the interstitial tissues.
Macrophages phagocytose red blood cells to
degrade haemoglobin into biliverdin, a green
compound, as well as carbon monoxide and iron.
The iron then forms haemosiderin with the ferritin
protein, creating a brown colour. Lastly, biliverdin
is rapidly metabolised to form bilirubin, which is
yellow in colour, signifying a bruise that is about to
disappear [1].
In criminal cases involving child abuse or
assault, it is common for forensic exper ts to
estimate the age of bruises based on the colour.
Since the conclusions of such analyses have the
potential to influence the outcome of convictions,
several studies were conducted on determining
the accuracy of these visual estimations. In 2010,
a simple study involved 11 participants voluntarily
inflicting bruises on themselves, all in the name
of science! Using a pump, suction was applied
to the skin to produce a uniform circular bruise
on each subject. Photographs of the bruise were
taken daily, and 15 forensic experts were asked to
estimate the age of the bruise and arrange the
photographs in chronological order.
It was found that as the actual age of the
bruise increased, the accuracy of the estimations
decreased [1]. In addition, many conclusions
made by the observers were extreme outliers.
Estimation accuracy was highest for freshly
inflicted bruises, between 0 to 12 hours, but
misjudgements occurred in every time group.
The results concluded that visual assessment of
photographs of bruises is an unreliable method for
estimating when bruises were inflicted.
What about speeding up the healing process
of a bruise? Popular home remedies include
unceremoniously slapping a piece of raw steak
on a shiner or repeatedly rolling an egg on a
stubborn bruise among other outlandish claims.
Unsurprisingly, the efficacy of steak masks is a
myth. What actually helps is the cold factor of the
frozen steak, since cold temperatures constrict
blood vessels and reduce inflammation or swelling.
In fact, placing raw meat on an injured area is
highly unadvised due to potentially dangerous
bacterial infections. Frozen steak can also cause
freeze injury around the wound. Applying an ice
pack would be a healthy alternative that gets the
job done.
Bruises are unsightly, painful and largely
unavoidable, but they are the body’s natural
process of healing. Whereas estimation of the
chronological age of a bruise based on its
appearance is not scientific, different colours of
the bruise divulge the processes involved during its
recovery. Scientists are racing to develop a reliable
system to provide more accurate estimations of
the chronological age of bruising.
