A dark spot rarely comes out of nowhere. Usually something set it off weeks or months earlier: a pimple you picked, a day at the beach, a hormonal shift, even a strap that kept rubbing the same patch of skin. Knowing what causes dark spots matters more than most people realise, because the trigger shapes how the mark looks, how long it hangs around, and whether a moisturiser and sunscreen are enough or a dermatologist should take a look.

Here are the common causes of dark spots and uneven-looking skin, in plain language.

First, a Quick Word on Melanin

Your skin colour comes mostly from melanin, a pigment made by cells called melanocytes. They sit in the lowest layer of the epidermis and pass melanin to the skin cells around them. Part of its job is protective: it absorbs some UV radiation and helps shield the cells underneath.

Sunlight, inflammation, injury and certain hormones can all push melanocytes to make more pigment. Evenly, that is a tan. In one spot, or with pigment settling deeper than usual, it becomes a darker patch. This is hyperpigmentation, and nearly every cause below works through it.

What Causes Dark Spots? The Main Triggers

1. Sun and light exposure

UV exposure is one of the most common triggers of extra melanin, and it also darkens marks that other causes have already left. Research also suggests that visible light, especially the high-energy blue-violet part of the spectrum, can deepen pigmentation in medium to deep skin tones. The sun deserves its own article, so the short version here: daily broad-spectrum sunscreen matters for almost every cause on this list.

2. Inflammation and skin injury (PIH)

This is the big one for many people in India. Post-inflammatory hyperpigmentation, or PIH, is the flat brown or grey-brown mark left behind after the skin has been inflamed or injured. According to the American Academy of Dermatology, common triggers include a pimple or psoriasis patch clearing, an insect bite, a cut or burn, and skincare products that irritate the skin.

Everyday examples include:

• Acne, especially squeezed or picked breakouts
• Eczema or dermatitis flares, including reactions to fragrance or hair dye
• Mosquito bites that were scratched, which is common during the monsoon
• Irritation from waxing, threading, shaving or epilating
• Harsh scrubs, strong peels or too many actives used at once
• Minor burns, from a hot pan or a curling iron, for example

Note that brightening products can create new marks if they keep stinging or peeling the skin. If you are dealing with marks after breakouts in particular, our guide on acne marks vs dark spots explains how to tell a red post-acne mark from true pigmentation.

3. Hormones and melasma

Melasma shows up as larger, fairly symmetrical brown or grey-brown patches, usually on the cheeks, forehead, upper lip or nose bridge. The AAD notes that rising oestrogen and progesterone during pregnancy are thought to trigger it, and that oral contraceptive pills can trigger it in some people. It is much more common in women, and it tends to run in families.

Sun exposure keeps melasma going, and heat is often discussed as a possible aggravating factor too. The evidence on heat is less settled than for UV, but some people find patches look worse after hot kitchens or intense summer weather. Melasma is often long-lasting and recurring, so get a dermatologist’s diagnosis rather than guessing.

4. Age and years of accumulated sun

Solar lentigines, often called age spots or sun spots, are small, flat, well-defined brown spots on skin that has seen years of sun: the face, backs of the hands, forearms and shoulders. They are not caused by age as such, but by UV exposure adding up over time.

5. Friction and repeated rubbing

Skin that is rubbed repeatedly can gradually darken: inner thighs, underarms, under bra straps or tight waistbands, elbows and knees. Heat, sweat and humidity worsen chafing, which is why it is so common in Indian summers. Looser fabrics and less scrubbing help more than any product.

6. Medications

Some medicines make the skin more sensitive to sunlight, so it burns or pigments more easily. Others can cause discolouration directly. DermNet lists certain antimalarials and tetracycline antibiotics among the drugs linked to pigment changes. If you notice new patches after starting a medicine, do not stop taking it on your own. Ask the doctor who prescribed it.

7. Underlying medical conditions

Occasionally, darker skin signals something internal. The NHS describes acanthosis nigricans as dark, thickened, velvety patches, usually in the neck, armpits or groin. It is often linked to insulin resistance, excess weight or type 2 diabetes, and sometimes to hormonal conditions. Thyroid and adrenal problems can also change skin colour. None of this can be fixed with skincare, so new, spreading or unexplained patches are a reason to see a doctor.

Causes of Dark Spots at a Glance

Why Deeper Skin Tones Are More Prone to PIH

Most Indian skin tones fall in the medium to deep range, where melanocytes tend to respond more strongly to inflammation. DermNet notes that PIH can happen to anyone but is more common in darker-skinned people, and that the colour tends to be more intense and last longer.

A pimple that leaves a faint pink mark on very fair skin can leave a brown mark lasting months on deeper skin. So preventing inflammation (treating acne early, not picking, not over-exfoliating) protects your skin tone, and gentler routines are safer than “stronger” ones. For how these causes fit together across the face, our beginner’s guide to uneven skin tone is a useful companion read.

Everyday Habits That Quietly Add Up

Small things can quietly make an existing cause worse: skipping sunscreen on cloudy monsoon days, harsh scrubs, lemon or toothpaste on the face, and waxing or threading skin that is already irritated. Pollution and hard water can leave skin feeling rough, but they are not a well-proven direct cause of distinct dark spots.

Once you know your likely trigger, the next step is a steady routine built around it. Our guide on building a skincare routine for dark spots covers that in detail, and you can browse products grouped by concern under dark spots and uneven tone.

Frequently Asked Questions

What causes dark spots on the face suddenly?

Marks that seem to appear suddenly are usually PIH from a recent breakout, bite or irritation, or pigmentation that darkened after unprotected sun exposure. New patches after starting a medication or during pregnancy may be linked to those changes. Anything unexplained or fast-changing is worth showing to a dermatologist.

Can stress cause dark spots?

Indirectly, possibly. The AAD lists stress as a possible melasma trigger, and stress can worsen acne and eczema, which can leave PIH.

Are dark spots from threading or waxing permanent?

Usually not. Irritation-related PIH typically fades over months, especially if the area is sun-protected and not irritated again. Spacing out sessions and soothing the skin afterwards can help prevent new marks.

When is a dark spot a reason to worry?

See a doctor if a spot changes in size, shape or colour, has irregular edges or several colours, bleeds, itches or does not heal, or if you notice velvety dark patches in skin folds. These need a proper medical check, not a cosmetic fix.

Reading the Clues Your Skin Leaves

So, what causes dark spots? Most come back to melanocytes reacting to a trigger: sun and light, inflammation, hormones, friction, medications or, less often, an internal condition. Where a spot sits and what came before it usually point to the cause. Calm the inflammation, protect your skin from the sun every day, keep your routine gentle, and let a dermatologist handle anything that looks unusual or keeps spreading.

This article is general cosmetic information and is not medical advice. For persistent, changing or unexplained pigmentation, please consult a qualified dermatologist.