Does Sun Exposure Help Eczema?

Hand reaching for sun.

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Atopic dermatitis, also known to as eczema, is a common chronic inflammatory skin disorder that affects between 1% and 3% of adults and 15% to 20% of children worldwide. The causes of eczema are complex but generally entail two factors:

  • A dysregulated immune system which alters the natural biome (ecology) of the skin
  • A reduction in the skin's barrier function due to genetic mutations that affect the production of structural proteins

In addition to developing itchy and inflamed skin, people with eczema are also more likely to develop skin infections, especially those involving the bacterium Staphylococcus aureus. This is why doctors focus on not only treating eczema but also preventing and treating secondary infections of the skin.

The good news is that there is one form of non-pharmaceutical treatment—natural sunlight—which may help combat both skin inflammation and infection.

Vitamin D and Eczema

Although it is not entirely clear why sunlight helps relieve atopic dermatitis, some scientists believe that vitamin D plays a central role. Sun exposure increases the production of vitamin D in the skin and, by doing so, helps modulate immune function in the outermost layer of skin (called the epidermis).

Key to this is an amino acid compound called cathelicidin that helps trigger the innate immune response (the body's first-line response to infection or any condition it considers abnormal). By increasing vitamin D production, sunlight indirectly increases the production of cathelicidin.

People with eczema characteristically have low concentrations of cathelicidin in the epidermis. Low concentrations confer to an increased risk of bacterial, viral, or fungal colonization. Even if these microorganisms do not cause an infection, their increased presence can lead to a worsening of eczema symptoms.

This may help explain, in part, why people with atopic dermatitis often get better with moderate sun exposure. Vitamin D supplements may further enhance this effect, particularly if one is nutritionally deficient.

Despite the suggestions of a benefit, the effect that vitamin D has on eczema remains unclear and subject to controversy.

A 2017 study from McGill University found that low vitamin D levels do not confer to an increased risk of eczema or increase the production of immunoglobulin E (IgE) that spur inflammation. Further research is needed to make sense of these contradictions.

Always check with your doctor before taking any vitamin D supplement. Dosages higher than 600 IUs per day should only be taken under the direction of a doctor. Overdosing can lead to nausea, vomiting, bone pain, and kidney problems.

Diagnosing Vitamin D Deficiency

It is wise to speak with your dermatologist before embarking on vitamin D supplementation. Your doctor may recommend that you take a blood test to ensure that you are, in fact, deficient. The most accurate way to measure vitamin D levels is with the 25-hydroxy vitamin D blood test.

Normal vitamin D levels are between 20 nanograms per milliliter (ng/mL) to 50 ng/mL. Anything less than 12 ng/mL indicates vitamin D deficiency.

Certain people are more prone to vitamin D deficiency than others and may inherently benefit from supplementation. Factors for deficiency include:

  • Being overweight or obese
  • Living in northern latitudes with low levels of sunlight
  • Having dark skin which decreases the absorption of UV radiation
  • Malabsorption disorders, such as celiac disease

While vitamin D deficiency often causes no symptoms, people who are deficient will often complain of fatigue, muscle weakness, and muscle pain. Over time, severe deficiencies can lead to an increased risk of fractures and osteoporosis.

If you avoid the sun because it makes your eczema worse, you may be at risk of vitamin D deficiency. Speak with your doctor if you are concerned or experience symptoms consistent with vitamin D deficiency.

Sunlight and Inflammation

Besides vitamin D production, sunlight may have other positive effects. Research has shown that exposure to ultraviolet (UV) radiation from the sun may help reduce inflammation in the skin. As a disease characterized by inflammation, eczema can't help but benefit from any therapy that safely alleviates this effect.

A 2017 study published in the Journal of Allergy and Clinical Immunology found that exposure UV light causes the release of nitric oxide into the bloodstream. Nitric oxide triggers an anti-inflammatory response by activating a cell known as a regulatory T-cell (Treg).

As per their name, regulatory T-cells regulate the immune response and help "put the brakes" on an overactive immune system. Because eczema is believed to be caused, at least in part, by an exaggerated immune response, it is theorized that activation of Tregs may help reduce symptoms.

Sunlight and Eczema Prevention

Some scientists also believe that the lack of sunlight may contribute to the rise in inflammatory skin conditions. The hypothesis suggests that, as modern society moves into a more indoor lifestyle, the lack of sunlight alters the skin's barrier function and dulls the body's natural inflammatory response. From an epidemiological standpoint, researchers are already seeing evidence of this.

According to research in the Journal of Nutrition and Metabolism, the incidence of eczema has increased by two- to three-fold in industrialized countries in recent decades, suggesting that lifestyle plays a role in its development.

Clinical evidence supports the hypothesis. A 2019 study from the University of Western Australia found that there was no difference in eczema between infants who were given vitamin D supplements compared to those who received none. What was discovered, however, was the infants who received less UV light exposure were more likely to have eczema.

This would suggest that UV exposure may play a more important factor in preventing eczema than vitamin D supplementation.

Phototherapy

Ultraviolet light treatments (also called phototherapy or UV light therapy) has been utilized as an adjunctive treatment for eczema for many years. It works by utilizing a device that exposes the skin to controlled bursts of UV-B or UV-A rays.

Phototherapy works similarly to natural sunlight but in a more controlled way. The procedure can be done at your doctor's office and is typically recommended when the first-line treatments of eczema (including topical steroids and immunomodulators) fail to provide relief.

Risks of Sun Exposure

Generally speaking, natural sunlight is considered safe with moderate exposure. This translates to between 10 and 30 minutes of sun exposure several times per week. People with darker skin may need a little more than this. The "ideal" exposure time will depend largely on how sensitive your skin is to sunlight.

Excessive sun exposure may cause more harm than good and only serve to exacerbate, rather than relieve, eczema symptoms.

Consequences of Excessive Sun Exposure

The risk of these conditions increases with long-term use of phototherapy treatments. Furthermore, people with atopic dermatitis may be more prone to sunburn when using photosensitizing agents like coal tar and tetracycline antibiotics common in eczema treatment.

Sun Safety Tips

While moderate exposure to natural sunlight may have obvious benefits, you should take care to do so safely. Start by speaking with your dermatologist to determine how much sun you can take per day and if there are any conditions you have (or medications you take) that may place you at risk.

If your doctor gives you the OK, there are a few tips you should follow:

  • Start by limiting your daily exposure. When first starting, limit yourself to five minutes of exposure and see how your skin reacts. If there is redness after a few minutes, you'll probably want to cut back until your skin is more tolerant. If there is no redness, tightness, or tingling, you can gradually increase the exposure over the course of days or weeks.
  • Avoid the sun between 11:00 a.m. and 3:00 p.m. This is when the sun is hottest and most likely to cause sunburn. Remember, the aim of the therapy is to reap the benefits of sunlight, not bronze your skin.
  • Use sunscreen. A high SPF sunscreen works by filtering out UV radiation. UV-A radiation is associated with skin aging, while UV-B is associated with sun burning. Using a sunscreen with an SPF rating of 25 to 30 allows for ample sun exposure while limiting damage to your skin.
  • Be aware that sunlight won't help all people. In fact, for some, sun exposure can make eczema worse. This is because heat and sweat are eczema triggers in some people. If your eczema tends to get worse when you are overheated (or during summer months), sun therapy might not be the best choice for you.
  • Avoid tanning salons. Tanning beds and booths utilize high doses of UV-A radiation which tans the skin quickly but increases the risk of skin cancer and premature aging.

A Word From Verywell

It is important to remember that sun exposure and vitamin D supplementation are only two of the many options one can pursue in the treatment of eczema.

Always speak with your doctor about any complementary therapy you decide to pursue. While you may assume that "natural" means "safe," it's not always the case. This is especially true where the sun is involved, especially if your eczema is severe or you are being treated with multiple drugs.

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Article Sources

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