Why red is the universal sign of danger

Travelling out of the city to join the expressway, the traffic light suddenly turned red. I stopped immediately. One, two, three minutes, the light remained on red. The line of cars behind me had grown and impatient drivers were hooting wildly trying to get me to proceed in defiance of the red light. Soon, the red light disappeared but was replaced by a black screen. Reluctantly, I made the move to drive on.

Fortunately, the coast was clear and no unsavoury incident occurred. About 10 miles into the journey, a petrol tanker ahead of us had caught fire, spewing hot red flames here and there. The entire road was abandoned and I had to make a detour to get to my destination.

As I was getting out of the car, my cousin ran out of the house, distraught and screaming, “Help me! Help! Help!” “What is it?” I asked. I was able to make out a few things out of her incoherent babble, “There is blood everywhere. She’s bleeding.” I did not wait to find out who was bleeding. I ran into the house ahead of her. I couldn’t believe what I saw.

Her two-year-old daughter was bleeding. The plug of the cannula (tube) that had been inserted into her vein by her doctor to give her antibiotic injections every 12 hours had come off and red blood was oozing out. The little girl and her four-year-old brother, totally oblivious of danger, were tickled at the sight of blood and dancing around it. I grabbed the little girl’s arm, quickly yanked off the cannula and applied some pressure on the site to stop the bleeding.

I then faced her mother and scolded her that she ought to have done what I did to save her child. Had I not walked in at that crucial moment, the little girl could have bled to death. As I spoke, something disturbing caught my attention. My cousin’s eyes were red and swollen. Suddenly I remembered the reason I was here. She had called me the night before to ask what she should use to treat her red eyes. I had asked a number of questions to which she was unable to give satisfactory answers.

Red eyes are a symptom of a wide variety of mild to serious diseases, disorders and conditions of the outer eye and other abnormal processes.  It can be a non-threatening condition, such as staying up late, tiredness or a small foreign body, such as an eyelash in the eye. Red eyes can also be the result of dryness of the eye or infection called conjunctivitis.

Often, it can be sight-threatening in conditions we call uveitis or acute glaucoma. My mind went through all these and more when my cousin asked me to recommend to her an eye drop she could use. Without examining her eyes, I could have done her a lot more harm because a wrong diagnosis or delay in treatment could actually result in permanent visual impairment or blindness in some of the conditions.

Making a diagnosis of the cause of red eyes is not easy. The exactness of the symptoms, a thorough medical history and physical examination, including a detailed examination of the eyes, are important. Quite often, a diagnosis cannot be made without special instruments such as the slit lamp, ophthalmoscope and measurement of the intra-ocular pressure.

In just one day, I was held up by a faulty red traffic light; lucky to escape the inferno of a burning petrol tanker; saved an innocent child from bleeding to death and attended to my cousin’s red eyes which could have resulted in severe visual impairment.

Unknown to me, the little boy had been listening with rapt attention to our conversation. He brought out his cell phone and showed me the picture of his mother’s eyes he had taken the night before.

“What if I had sent this to you over the internet, would it have helped in reaching a conclusion as to the cause of mum’s red eyes?” Without waiting for an answer, he added ruefully, “Mum didn’t let me send this picture.

She felt it was unnecessary.”  I told him it might have helped and it was ingenious for him to have thought about it. Pictures are occasionally good substitutes for physical presence of a patient, “But don’t you think my presence here today has been a big blessing?” “Yes doctor, you saved my sister.  I didn’t know that she was in serious danger.”

“One more question, doc. Why is red the universal sign of danger?” The little boy asked. “Do I really have enough time to explain to this inquisitive boy?” I answered, “Red is the colour of fire and you know what happens when you put your hand in fire! It is also the colour of blood and you know when someone loses a lot of blood, he may die.

These are universal experiences. So, red is associated with danger everywhere. The scientific explanation is also simple: visible light (or simply light) consists of seven colours – red, orange, yellow, green, blue, indigo, and violet. Of all the colours, red is scattered the least by air molecules and therefore makes the best impression.”