How does sun exposure affect melasma?

Why does sunlight darken melasma?

Melasma develops when melanocytes, the cells that make skin pigment, become more active. They produce melanin, the pigment that gives skin its color. UV exposure stimulates extra melanin production, contributing to darker patches. Melasma commonly appears on the cheeks, forehead, nose and upper lip, often in a symmetrical pattern. Sunlight is one trigger rather than the only cause: family history and hormonal changes, including pregnancy and contraceptive use, also matter. Melasma can affect anyone, although it is especially common in women with brownish skin tones.1234

Which sunscreen should you choose?

Choose a tinted, water resistant, broad spectrum sunscreen containing iron oxide. SPF 30 is the minimum; SPF 50 or higher is a useful choice for exposed skin with pigmentation. Broad spectrum protection covers UVA and UVB. SPF describes UVB protection, so the largest number on the bottle is not the whole job description. Many sunscreens protect against UV without protecting against visible light. Visible light can worsen melasma, especially in darker skin tones, making the tint more than a cosmetic preference.2356

How to protect your skin each day

1. 1Apply sunscreen in the morning before going outside. Allow at least 15 minutes before sun exposure, and follow your product's application directions. Cover all skin not protected by clothing, including frequently missed areas such as the ears.
2. 2Make protection a daily habit, including cloudy days and winter. Brief outings still count: even a little sun exposure can worsen melasma.
3. 3Add a wide brimmed hat and seek shade outdoors. Look for a hat with a UPF rating, which describes the fabric's UV protection; UPF 50 or higher is a good choice.
4. 4Reapply sunscreen at least every two hours while outdoors. Reapply after swimming and more often with heavy sweating rather than relying on the morning application to last.
5. 5Reduce time in direct sun during midday. In summer, peak sunshine hours are roughly 10 am to 4 pm. Avoid intentional tanning, tanning beds and sunlamps.

Sun protection includes shade and clothing as well as sunscreen, so the bottle does not get to take all the credit. Neither sunscreen nor protective clothing blocks all UV radiation. Reflected sunlight near water, sand or concrete increases exposure, and higher altitudes require extra care. Plan protection around where you will be, not just whether the weather feels sunny.15

Will sun protection make melasma disappear?

Sun protection helps limit further darkening and supports treatment, but melasma can persist for years and often returns. There is no fixed fading timetable. Melasma associated with pregnancy or hormone medicines often fades over several months after pregnancy ends or the medicines are stopped, but sun exposure can bring it back. Discuss any medicine changes with your prescriber. If patches remain bothersome, a dermatologist can assess the triggers and plan treatment alongside continued sun protection.124

What if skincare makes the patches worse?

Choose gentle products without fragrance, and stop using a product that burns or stings: irritation can darken spots. Excessive or improper use of hydroquinone, retinol and alpha hydroxy acids can worsen upper lip melasma. Ask a dermatologist before escalating those products or booking peels or laser treatment, which can cause further pigmentation. Persistent facial darkening also deserves an examination, because other pigmentation disorders can resemble melasma.2347