Millions of people around the world suffer from autoimmune diseases, and one of the most common parts of the body affected by an out-of-control immune system is the skin. Several autoimmune diseases can affect the skin, such as scleroderma, psoriasis, dermatomyositis, alopecia areata, vitiligo, and lupus erythematosus.
As we all know, the immune system can be activated or inhibited by several factors, both internal and external to the body (1). Scientists have actually found that the sun and its ultraviolet radiation is one of the main environmental factors that affects these diseases (2). Therefore, learning what role the sun plays in their development and how to protect yourself is a crucial step to keeping your autoimmune disorder under control.
In this article, we will be looking at lupus and at exactly how UV radiation plays a part in its progression.
What is lupus erythematosus?
Lupus erythematosus actually refers to a group of autoimmune diseases in which the human immune system becomes hyperactive and attacks healthy cells. Usually, there are periods of illness, called flare-ups, and periods of remission during which there are very few symptoms (3). This collection of conditions is commonly divided into two main groups:
There is one similar trait among every single type of lupus and that is that these people are photosensitive. This means that exposure to the sun worsens the appearance of their skin lesions or incites flare-ups (8). But, why is the sun a lupus patient’s number one enemy?
What is photosensitivity?
While all humans are sensitive to the sun and even healthy skin will react if exposed to its rays for too long, photosensitivity is a term used to describe anything outside of the normal range of reactions (9). Photosensitivity or sun sensitivity, thus, applies to anyone who develops inflammation when exposed to ultraviolet radiation (10).
In fact, photosensitivity is such an important factor in lupus that it triggers cutaneous flare-ups as well as systemic symptoms and is considered one of the 11 diagnostic criteria for the disease by the American College of Rheumatology (11).
The mechanisms linked to photosensitivity might include: modulation of autoantibody location, cytotoxic effects, apoptosis induction, upregulation of cytokines, nitric oxide, and tumor necrosis factor α, to name a few (12).
However, certain studies have shown that different types of radiation produce inflammation through different pathways (11). UV radiation is divided into UVA, UVB, and UVC. For many years, it was thought that UVB was the one responsible for causing photosensitivity in lupus patients. Nowadays, it is known that both UVA and UVB radiation have a role to play in its progression (6).
This is, in part, caused by the UV-induced expression of certain proteins. One known protein called “Ro” is abnormally expressed on the surface of cells after the skin is exposed to UV. This protein draws white blood cells to the area, inciting them to attack healthy skin cells (7).
Thus, UV irradiation can cause an acceleration in the apoptosis, or programmed cell death, of skin cells and also contributes to the accumulation of apoptotic cells in the skin of lupus patients (13). When these dying or dead cells are not cleared from the skin properly, they trigger the release of a secondary chain of proinflammatory agents.
The distribution of skin lesions in sun-exposed areas and a delay of their onset of more than 48 hours after the exposure are both characteristic symptoms of lupus (14). Therefore, photoprotection is essential in the treatment of these patients.
How can lupus patients protect themselves from the sun?
There are many ways in which these photosensitive people can avoid the sun. They must remember to protect themselves from both UVB and UVA radiation, wear protective clothing, and apply topical broad-spectrum filters.
Lupus patients are recommended to exercise sun avoidance from 11 am to 3 pm during the summer months, as these hours include the most intense radiation (15). They would also do well to remember that car and house windows do not filter UV rays (6). Also, water is a reflective surface. So, staying in the shade at the beach is not a sufficient method of sun avoidance.
Another method to combat photosensitivity which has been gaining ground in recent years is the use of oral and topical antioxidants to counteract the toxic effects of UV exposure (10). For example, green tea contains polyphenols, which are naturally occurring compounds known for their antioxidant activity. One study showed that daily consumption of green tea extracts improved lupus disease activity as well as some aspects of quality of life (16).
Beta-carotene has also been shown to reduce the effects of photosensitivity. It has even been reported that an intake of 50mg of beta-carotene three times daily for merely one week is enough to see visible improvement of lupus lesions (17).
As you can see, photoprotection is a crucial step in the treatment of lupus erythematosus. Wearing sunscreen, avoiding peak hours of UVR, and adding a couple of antioxidant supplements to your diet can not only improve the appearance of your skin; it can improve your quality of life.