Skin spots: why they appear and when we should seek medical advice

Why do spots appear on the skin?

The color of our skin depends on different factors, but one of the main ones is melanin, a pigment produced by cells called melanocytes.

Melanin plays an important role in protecting our skin from ultraviolet radiation.

When its production or distribution changes, we may notice darker or lighter areas.

But not all spots depend on melanin.

A red area may be related to inflammation or vascular changes.

A white spot may represent a decrease or absence of pigmentation.

And a brown lesion can range from a completely benign lesion to one that needs to be investigated.

That is why color alone does not establish a diagnosis.

Brown spots: are they always caused by the sun?

No.

But the sun is one of the most important factors.

Over the years, cumulative exposure to ultraviolet radiation can encourage the appearance of solar lentigines, especially on the face, décolletage, shoulders, and backs of the hands.

These are the spots that many people simply call 'age spots.'

In reality, they have a great deal to do with our history of sun exposure.

There are also other causes of pigmentation, such as melasma, post-inflammatory hyperpigmentation, and various melanocytic lesions.

That is why two apparently similar brown spots can have completely different origins.

What is melasma?

Melasma produces areas of brown pigmentation, often quite symmetrical, especially on the face.

It can affect the forehead, cheeks, upper lip, and other facial areas.

Sun exposure plays a fundamental role, and hormonal and genetic factors are also involved.

That is why it is particularly common in women and can appear or worsen during certain hormonal stages.

And here an important concept emerges: not all spots are treated the same way.

Applying a laser indiscriminately to any facial pigmentation may not be the right strategy.

First, we need to know what we are treating.

Why can inflammation leave a spot?

After certain skin inflammations, the skin can produce residual pigmentation.

This is called post-inflammatory hyperpigmentation.

It can occur after acne, dermatitis, trauma, burns, and certain procedures.

Even though the original inflammation has disappeared, the pigmentation can remain for weeks or months.

That is why patients sometimes say: 'The pimple is gone, but it left a mark.'

The active lesion has disappeared. What we see now is its pigmentary consequence.

What do white spots on the skin mean?

White spots on the skin also have numerous causes.

One of the best known is vitiligo, a disease in which functional melanocytes are lost and depigmented areas appear.

But not every white spot is vitiligo.

We can also find hypopigmentation related to other dermatological conditions, prior inflammation, superficial infections such as pityriasis versicolor, and small spots associated with photoaging, among other possibilities.

That is why searching for white spots on the skin should not automatically end in a self-diagnosis of vitiligo.

What about red spots on the skin?

Exactly the same applies to red spots on the skin.

Red usually indicates that we are observing phenomena different from melanin pigmentation.

There may be inflammation, dilation of blood vessels, dermatitis, infections, drug reactions, and numerous dermatological conditions.

An isolated red spot that persists for months is not interpreted in the same way as dozens of red spots that have appeared suddenly all over the body.

Context matters just as much as color.

Can a spot be skin cancer?

Yes.

But this does not mean that every dark spot is a melanoma.

When patients search for expressions such as skin cancer spots or spots skin cancer, there is usually a specific concern: "How do I know if my spot is dangerous?"

We cannot diagnose a skin cancer based solely on a description found on the Internet.

However, there are signs that should catch our attention.

Melanoma, for example, can present as a new lesion or as a pigmented lesion that begins to change. It can also appear in areas that receive little or no sun exposure.

The ABCDE rule

A simple tool for learning to observe certain pigmented lesions is the ABCDE rule.

A – Asymmetry. One half of the lesion does not look like the other.

B – Border. The borders are irregular, poorly defined, or have uneven shapes.

C – Color. There are different colors within the same lesion.

D – Diameter. Traditionally we pay attention to lesions larger than approximately 6 mm, but this is important: a melanoma can be smaller.

E – Evolution. Probably one of the most important criteria. A lesion changes in size, shape, color, or appearance over time.

The American Academy of Dermatology uses precisely these criteria as warning signs to detect possible melanomas.

The E for evolution deserves special attention

A photograph taken six months ago can be extraordinarily useful.

Why?

Because our visual memory is not perfect.

Many times we look at a lesion every day and do not notice small, gradual changes.

That is why a lesion that is changing deserves attention even if it does not perfectly meet all the other ABCDE criteria.

The 'ugly duckling' rule

There is also another very useful concept.

Imagine you have numerous moles that look quite similar to one another.

But one is completely different. Darker. More irregular. Larger. Or simply does not resemble the others.

That 'ugly duckling' deserves to be observed with special attention.

The AAD specifically recommends evaluating lesions that are new, different from the rest, or that evolve, itch, or bleed.

Does a lesion have to hurt to be dangerous?

No.

This is a common misconception.

A melanoma may cause no pain or discomfort whatsoever.

That is why: 'It doesn't hurt' does not mean 'it is benign.'

A lesion may require evaluation even if it is completely asymptomatic.

What if it bleeds?

A lesion that bleeds spontaneously, forms a wound that will not fully heal, or changes repeatedly deserves an evaluation.

This does not automatically mean cancer.

Many benign lesions can become irritated or bleed after trauma.

But a persistent lesion that bleeds, grows, or does not heal should not be ignored.

Should we only look at sun-exposed areas?

No.

And this is especially important.

Skin cancer can appear in areas that receive little solar radiation.

We must also remember the palms, soles of the feet, scalp, and nails.

In certain skin phototypes, some forms of melanoma occur proportionally more often on the palms, soles, or nail region.

That is why a new or changing pigmented line beneath a nail may also require a dermatological evaluation.

How does a dermatologist examine a spot?

First, we observe the lesion.

But our eyes are not the only tool.

We frequently use dermatoscopy.

The dermatoscope allows us to visualize structures and patterns within a lesion that we cannot adequately appreciate with the naked eye.

This helps differentiate numerous benign lesions from those that present suspicious characteristics.

When a lesion remains suspicious, we may recommend its excision or biopsy in order to perform a histological examination.

Because the definitive diagnosis of certain lesions is not made by looking at a photograph: it is made by studying the tissue.

Do all spots need treatment?

No.

And we must distinguish between two concepts: diagnosing a spot and removing a spot. They are not the same thing.

A completely benign lesion may be removed for cosmetic reasons.

Another may simply be observed.

A suspicious lesion first requires an appropriate diagnosis.

That is why, before using laser, peeling, or any other procedure to remove a pigmented lesion, we need to know what we are removing.

In Dermatology, erasing a spot without first diagnosing it can mean erasing important clinical information.

How can we prevent sun-related spots?

Photoprotection is essential.

And it does not consist solely of applying sunscreen when we go to the beach.

It includes reducing intense sun exposure, wearing clothing, hats, and other physical protective measures when appropriate, seeking shade, and correctly using a suitable photoprotector.

Cumulative ultraviolet exposure not only plays a role in pigmentation.

It also contributes to photoageing and the development of various skin cancers.

When should I see a dermatologist about a spot?

We do not need to rush to the dermatologist for every new freckle.

But a lesion deserves evaluation — especially if it: appears newly and keeps growing; changes in size, shape, or color; looks clearly different from the others; displays multiple colors; bleeds without a clear explanation; itches persistently or hurts; forms a wound that does not heal; or simply raises concern because it is changing.

A new, different, or evolving lesion is precisely one of the main reasons to seek a dermatological evaluation.

What I want you to remember

When we observe spots on the skin, color is only the beginning of the story.

A brown spot can be a consequence of sun exposure.

A white spot may correspond to vitiligo or have many other causes.

A red spot can represent an inflammatory, vascular, or entirely different dermatological process.

And a pigmented lesion can be benign or — far less commonly — require ruling out a skin cancer.

That is why I do not want you to look at every spot with fear. I want you to learn to observe how it behaves.

Is it new? Is it changing? Does it look different from the others? Does it bleed? Does it not heal?

Because in Dermatology there is a simple rule worth remembering: a spot is not diagnosed by its color alone.

First we establish what it is. And only then do we decide whether we should monitor it, treat it, or remove it.