Blue nevus - Do I need to worry if I have a blue mole on my skin?

Moles, also called nevi, can appear on the skin in different shapes, sizes and colors. A very characteristic type is the blue nevus or blue mole which is named for its characteristic color. 

Although these types of moles are not frequent, are usually benign and are not a cause for concern. However, as in any other it is important to monitor the mole to see if it changes shape or size over time.

Keep reading this article to learn more about these moles and the research studies we are conducting to learn more about them. 

Abstract blue watercolor

What is a blue nevus?

A blue mole is made up of the same cells as the rest of the moles, the melanocytes. 

Interestingly, the blue color is due to the pigment being deeper in the skin than ordinary moles and not because it is actually blue. This physical characteristic is called the Tyndall effect and is responsible for the blue color of these moles. 

Diagram showing the differences between a normal nevus and a blue nevus.

Because the pigment is relatively deep, it is susceptible to the Tyndall effect. That is, there is selective absorption of the longer wavelengths of light by the deep dermal pigment, with reflection from the skin to the eye of the shorter (blue) wavelengths. 

What do blue polka dots look like?

Blue nevus has a characteristic blue-blackish color and usually presents as a single lesion of 0.5 to 2 cm anywhere on the body. 

Here are some images so you can see what these blue polka dots look like. 

Clinical imaging

Dermatoscopic images

Why does a blue mole form?

Most blue nevi appear during the first four decades of life and are rarely present at birth. For reasons that are unclear, women are more likely than men to develop a blue nevus. 

Due to the variation in the frequency of blue nevi in different populations, a genetic predisposition has been suggested. However, familial cases of blue moles are extremely rare.

Is a blue mole dangerous?

A blue nevus is not dangerous at all and you can have a benign blue nevus on your skin for your entire life. However, on some occasions there may be malignant lesions that can simulate a blue mole.. That is why in some situations, which I will discuss below, it is advisable to see a dermatologist to check this type of mole.

Most important signs to see a dermatologist if you have a blue mole

In summary, blue moles that develop and begin to grow in adulthood may be cause for concern. If you get a blue nevus or other mole after the age of 30 it is best to have it checked out in the office. It may be a sign of skin cancer such as melanoma.

In addition, we have seen that blue moles are very stable over time and changes or growth is rare. Therefore, if we observe changes in blue nevi, it would be advisable to see a dermatologist to check them. 

All of the following characteristics of blue nevi are sufficient reason to request an appointment with a specialist to rule out malignancy:


  • It has an asymmetrical shape
  • Has irregular edges
  • Change color over time
  • Grow in size or are larger than 6 millimeters
  • Protrude from the skin
  • Are annoying, painful, itchy or bleeding

If you notice any of these changes, go to your dermatologist to evaluate you.

Is it necessary to remove a blue nevus?

Blue moles are benign lesions and are it is not necessary to remove them if the diagnosis is clear.

If there is doubts about the diagnosis, a complete excision may be considered. of the entire lesion. The melanocytes of a blue nevus are usually quite deep and a superficial biopsy by shaving or attempting to remove them by laser is not possible. 

You can also talk to your dermatologist about the removal if the mole is causing you discomfort. For example, if it rubs against your skin or causes other types of irritation.

If the blue nevus reappears after removal, contact your dermatologist. It could be a sign of skin cancer.

Blue nevus research

Together with our research team of the Hospital Clínic de Barcelona we developed the first cohort study to assess the change in the growth of blue moles. 

For this purpose, we used image databases of more than 22 years and, by means of artificial intelligence tools, we were able to achieve identify blue nevi among more than 1,000,000 images. Thanks to the intensive follow-up we performed on our patients on a regular basis, we were able to measure the change in size of blue moles over many years. Finally, we were able to plot and explain how this peculiar type of mole behaves. 

Diagram showing the growth pattern of blue nevus or blue mole.

As a conclusion of the study, we could observe that most of the blue nevi are very stable over time and their size does not change (blue lines). In some less frequent cases, we observed a discrete growth of less than 100%. Only in 2 cases did we see a very rapid growth that required excision of the lesion. to rule out a malignant mole and in these cases we are studying the molecular biology of these tumors.

Blue mole - my findings

Blue polka dots are benign skin lesions and usually appear during the first decades of life. 

But if the mole appears later in life (after the age of 30), or if a previous blue mole starts to gradually change over time, you must see your dermatologist to rule out malignancy

If we decide to remove the mole we will always perform a histological study. This way we can verify the diagnosis, and in the rare case that it is malignant, we can advise you on the steps to follow.

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Sebastian Podlipnik - Skin cancer

Sebastian Podlipnik

Dermatology Blog

I am a dermatologist and cum laude MD and author of multiple research studies. I specialize in skin cancer, laser technologies and cosmetic dermatology. The intention of this blog is to bring you closer to topics of interest in dermatology and research.

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