Rubbing Salt in The Wound


As you are no doubt aware, the idiom ‘rubbing salt in the wound’ refers to making an already painful or dire situation even worse, but medically, salt is used in the form of saline to sterilise wounds, due to the hydrophilic properties of sodium chloride – the salt in saline absorbs moisture from the wound that would otherwise enable bacteria to proliferate.

Unfortunately, despite containing roughly the same proportion of salt to water, the ocean is not a sterile environment, since there are certain bacteria that thrive in the ocean that would not be introduced in a sterile environment, Staphylococcus aureus among these.

So why is rubbing salt in a wound so painful? To understand this question, we have to look at the system with which the body identifies pain. An impulse is triggered by sensory receptors in the skin which allow sodium ions to enter the neuron. This increases the resting potential (around -70mV) which gives rise to a generator potential, initiating an action potential – the wave of depolarisation. This travels along the axon of the neuron until it reaches the end, at which point there is a synaptic knob, followed by a synapse.

Nerves would be surrounded by a significantly greater concentration of Na+ ions which allow for a higher frequency of nervous impulses since there are more waves of depolarisation (and subsequent re-polarisation) within the axon of the nerve cells. This constitutes a stronger sensation of pain, hence the stinging when salt is applied to wounds.

In terms of treatment of wounds, there is no real medical benefit to using salt, since clean water is much less painful and does much the same thing. Since there is potential to promote proliferation of halophiles (salt-loving bacteria) it is recommended that salt not be rubbed into your wounds, especially in the case of the ocean.
I hope you found this article interesting and informative.

By Louis Lane.

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