Vitiligo: Is sun exposure dangerous?

Can sun exposure promote the progression of vitiligo?

The vitiligo is an autoimmune disease characterized by the destruction of melanocytes, the cells responsible for melanin production, thereby causing depigmentation in certain areas of the body. Although genetic predispositions play a major role in its development, several environmental factors may also promote the onset of vitiligo. Among these, sun exposure is cited as a potential trigger, due to the oxidative stress it can induce within melanocytes.

However, phototherapy is one of the most commonly used approaches to promote repigmentation of vitiligo lesions.

PUVA phototherapy, combining psoralen and UVA radiation, acts by modulating the immune response, notably by reducing T-cell activity. Meanwhile, narrowband UVB (NB-UVB) phototherapy stimulates the proliferation and migration of melanocytes still present in adjacent areas. However, uncontrolled sun exposure can trigger sunburns or localized inflammation, which may exacerbate existing lesions, particularly via the Koebner phenomenon, where skin trauma leads to the development of new patches.

A study conducted on 442 vitiligo patients, distributed across various phototypes (I to VI), examined their perception of sun-exposure risk. Among them, 86 patients reported that their patches appeared more visible after exposure, and 113 thought their depigmented areas were more vulnerable to sunburn. These findings reflect a common experience among patients. Moreover, many of them often believe that vitiligo increases the risk of developing melanoma.

Contrary to what one might assume, vitiligo appears to diminish cancer occurrence, since the autoimmunity induced in vitiligo seems to confer protection against melanomas. Additionally, vitiligo patients often demonstrate better reflexes in photoprotection.

Indeed, a large-scale study conducted in 2014 analyzed a cohort of 10,040 vitiligo patients to assess their risk of skin cancer compared with a control group. The results revealed a significantly lower incidence of skin cancer among individuals with vitiligo. However, the study also highlighted a higher risk of skin cancers in patients who had undergone phototherapy sessions (14.1% versus 3.2%).

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3.8% and 1.1%

These were the respective risks of nonmelanoma and melanoma skin cancers in individuals with vitiligo.

19.6% and 4.5%

It concerned the risk of non-melanoma and melanoma skin cancers in individuals without vitiligo.

Does sun exposure increase the risk of vitiligo?

Another common misconception is that sun exposure promotes the development of vitiligo in individuals with no pre-existing lesions.

A study published in the Journal of Investigative Dermatology with 51,337 participants found that individuals with a high tanning capacity, that is, a dark phototype, may have an increased risk of developing vitiligo, due to a genetic variation in the TYR gene, which encodes tyrosinase, a key enzyme in melanogenesis. Additionally, reduced levels of glutathione peroxidase (GPx), an enzyme essential for neutralizing reactive oxygen species responsible for oxidative stress—a factor implicated in the onset of vitiligo—have been observed in these women. This correlation may help explain their higher susceptibility to the disease.

Research also suggests that individuals who experienced severe sunburn after more than two hours of sun exposure in childhood have an increased risk of developing vitiligo. A study published in the British Journal of Dermatology revealed that, among 177 patients surveyed, 51 identified the sunburns as a trigger for the disease, meaning that the initial depigmented lesions appeared shortly after the severe sunburn. However, the small participant pool and the subjective nature of these accounts prevent definitive conclusions.

When exposed to UV radiation, the skin undergoes cellular stress that leads to the production of heat shock proteins, notably HSP70i. Overexpression of this protein has been linked to a depigmenting autoimmune response that may stimulate immune-mediated attacks on melanocytes. Severe sunburns from prolonged sun exposure could thus initiate a cascade involving HSP70i, promoting both an autoimmune response and oxidative stress, which exacerbates cellular damage. Furthermore, the Koebner phenomenon—a process in which skin trauma fosters the emergence of new vitiligo lesions—may also contribute to disease development.

However, additional studies are necessary to confirm these mechanisms and to better understand the link between sun exposure and the onset of vitiligo.