Nail discoloration isn't an uncommon occurrence. Changes in color and appearance are ways in which your body tries to communicate that something is wrong.

A lot of the time, the discoloration is due to dehydration, bruises or a fungal infection, but every so often it is a sign of more serious illnesses like diabetes, kidney, heart or lung conditions and even cancer.  

A few weeks ago, Jean Skinner, a beauty technician from East Sussex, England, had a walk-in client come in for a manicure. The woman asked for her nails to be painted with a dark polish because she wanted to cover a black line running down the middle of one of her nails.

The client was convinced that the dark mark was harmless and chalked it up to a blood blister or the "lack of calcium," but it turned out to be much more serious. Now Skinner, with permission from her client, is using the experience to warn others.

Keep reading to find out what caused the dark line on the woman's nail.

As soon as Skinner saw the abnormal pigmentation on her client's nail, she knew it was beyond a normal bruise.

She didn't want the woman to panic, so she simply suggested that she get the finger examined by a doctor. It turned out to be melanoma, the deadliest form of skin cancer.

"This is melanoma!!! I did not want to frighten her but I told her she needed to see her doctor immediately!" Skinner wrote in a Facebook post. "She called me today to tell me that yes it was a very aggressive melanoma that has already spread to her lymph nodes!! Her prognosis is not good![sic.]"

Apparently, the vertical line has shown up on the woman's nail for a while now, but previous nail technicians she's worked with brushed it off.

Now, Skinner is urging people to pay better attention to abnormalities in their nail beds because even if the changes "can very likely be nothing to worry about," sometimes it is "an indication of a very serious disease."

After Skinner's post started to circulate, other people started to share their own stories. One reader commented:

"I have recently had top half of my thumb amputated as a result of a black mark on my nail which turned out to be a malignant melanoma. Please take this warning seriously as this form of cancer is very aggressive.[sic]."

These women's stories are a reminder that no matter how small the dark line on your nail bed is, it should always be checked by a specialist to rule out the possibility of subungual melanoma.

Skinner also noted that we should watch out for these signs in our loved ones, especially the elderly.

You can read Skinner's entire post below:

Please remember to share this warning with your loved ones. It could save their life.