The myth
Hyperpigmentation is caused by the sun. If you protect yourself from UV, the dark spots will fade and new ones will not form.
Why people believe it
Because UV genuinely is the single most documented trigger. It shows up in every dermatology textbook, every product label, every "how to fix dark spots" article. The advice is consistent and emphatic: wear sunscreen, avoid peak hours, protect your skin from UV. And that advice is correct. UV does activate melanocytes. It does sustain existing pigment. Nobody is arguing otherwise.
The problem is the word "only." When the messaging is overwhelmingly focused on one trigger, people reasonably conclude it is the trigger. Everything else gets treated as secondary, if it gets mentioned at all.
What else activates pigment
UV is one entry point into a process that has several. Melanocytes respond to any stress signal the skin registers as a threat. UV happens to be the most studied, but it is not the only one producing results.
Heat activates melanocytes through the vascular system and through TRPV1 receptors in the skin. No UV required. Cooking over a hot stove, a steam room, a laptop on your legs, or a humid climate can all trigger pigment through pathways that sunscreen does not touch.
Inflammation is the mechanism behind post-inflammatory hyperpigmentation. A breakout, an eczema flare, a razor nick, an irritating product: any event that creates inflammation sends signalling molecules to melanocytes. The pigment that follows is not caused by the sun. It is caused by the skin's own inflammatory response.
Hormonal shifts drive melasma and pregnancy-related pigmentation through oestrogen and progesterone pathways that interact with melanocyte receptors directly. These triggers operate regardless of UV exposure. Sun makes them worse, but it does not create them.
Friction and mechanical trauma from clothing, hair removal, or repetitive rubbing can activate pigment in areas that never see sunlight.
Internal factors like blood sugar regulation, thyroid function, gut health, nutrient deficiencies, and chronic stress all feed into the inflammatory and oxidative signalling that keeps melanocytes active. These operate systemically and have nothing to do with what is happening on the surface of the skin.
Why this myth stalls progress
When someone builds their entire strategy around UV, the other triggers keep running in the background. They are wearing SPF 50 every day, reapplying diligently, avoiding midday sun. And the pigment does not improve, or it improves slightly and then comes back. The conclusion feels obvious: the sunscreen is not strong enough, or their skin is just "difficult."
Neither is usually the case. What is more likely is that another trigger, one the sunscreen was never designed to address, is still active. Hormonal signalling. Low-grade inflammation from an over-aggressive routine. Heat exposure nobody thought to ask about. An internal factor that has never been identified.
The fix is not to stop wearing sunscreen. UV protection is still the foundation. The fix is to stop treating it as the entire strategy. When someone identifies and addresses the other active triggers alongside UV protection, things that had been stuck for months often start moving.
The opposite extreme is not the answer either
Some people overcorrect from "just use sunscreen" into total sun avoidance. Staying indoors all day. Refusing to go outside without full coverage. Treating any light exposure as a setback.
That level of avoidance is not sustainable and it is not necessary. What matters for pigment management is reducing unprotected cumulative exposure, not eliminating all contact with sunlight. A well-protected walk outside is not going to undo months of progress. But the anxiety of trying to avoid all sun often leads to the thing that actually does set people back: burnout and non-compliance. Someone who decides the rules are too strict eventually stops following any of them.
The goal is consistent, realistic protection as part of a broader approach that addresses all the active triggers, not just the one on the label.
UV is the most documented trigger. It is not the only one. If your strategy starts and ends with sunscreen, it is not a complete strategy.
