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Burning sensation
Why does salt, when applied on to an open wound, produce a burning sensation?
D. Epiphany Pushparaj Vincent
Vellore, Tamil Nadu
Normally the receptors over the skin for touch, pressure, pain, heat are placed in the deep places, in the dermo-epidermal junction. These receptors are named as Pacinian corpuscle, Krouse end bulbs and bare Nerve endings.
Paciniancorpuscle and free nerve endings are responsible to feel touch and pain sensation. Krouse end bulbs are meant for thermal sensation. Burning sensation are admixture of pain and thermal sensation.
Extremes of thermal sensation are painful. The bare nerve endings are present in the body openly in cornea and glanspenis and touching these highly sensitive areas is really pain full. A wound is an area where all the receptors for pain and temperature are exposed freely.
On application of any irritant chemicals on the wound they cause electrolyte transmission like sodium, potassium, calciumions influx across the nerve receptors causing electrochemical discharges which send nerve impulses to the spinal cord and from there to the brain where pain or burning sensation are appreciated.
In places, where there are bare nerve endings, as specified above, even if there is no wound, application of salt and other irritant chemicals causes pain sensation.
Non irritant chemicals like chlorhexdene, plain iodine (without spirit) do not cause any pain or burning sensation while applied to wounds.
Where there are no pain receptos exposed, like intact skin, all these soft chemicals do not cause pain or burning sensations, unless the skin is disrupted owing to corrosion etc, as any acid does.
Dr. Nagarajan Venkataraman
Professor Emeritus in Neurosciences
Dr MGR Medical University
Tamil Nadu
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