Does Sun Exposure Help Eczema?

Hand reaching for sun.

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Atopic dermatitis, most commonly referred to as eczema, is a common chronic inflammatory skin condition in infants and children that also affects about 1% to 3% of all adults. The causes of eczema are complex, but generally, entail two factors:

  • A dysregulated immune system
  • Deficiencies in a person's skin barrier

In addition to the itchy, red, and inflamed skin rash of atopic dermatitis, people with eczema are also more likely to develop skin infections, especially with the bacteria Staphylococcus aureus. This is why doctors focus not only on treating a person's inflamed, irritated skin in atopic dermatitis, but also on preventing and treating skin infection.

The good news is that one type of treatment that may help combat both skin inflammation and infection is judicious exposure to sunlight.

Vitamin D and Eczema

It's not completely clear why sun exposure helps atopic dermatitis, but one 2008 study suggests that vitamin D may play a role, as sun exposure increases vitamin D production in the skin. More specifically, supplementation with oral vitamin D appears to increase the production of cathelicidin in the skin of people with atopic dermatitis.

Cathelicidin is a protein that protects against skin infections from viruses, bacteria, and fungi in healthy skin. People with atopic dermatitis have low amounts of cathelicidin in their skin. These lower levels may result in colonization and infection of the skin with bacteria, viruses, and fungi, which is known to worsen eczema in people with atopic dermatitis.

The increased production of cathelicidin may explain why people with atopic dermatitis often get better with moderate amounts of sun exposure. Vitamin D supplementation may further enhance the effect, particularly if you are nutritionally deficient.

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

Despite this information, the effect vitamin D has on eczema is still unclear and the research provides a mixed bag.

There are some studies that have found low vitamin D levels do not seem to trigger eczema development. What's more, other studies have found that high levels of vitamin D are also linked to eczema development.

Diagnosing Vitamin D Deficiency

It is always wise to speak with your dermatologist before embarking on sun exposure therapy. Your doctor may recommend a vitamin D blood test first, to ensure that you are indeed deficient. The most accurate way to measure vitamin D 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 (see below).

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

  • Obesity
  • Living in northern latitudes with low levels of sunlight
  • Having dark skin which decreases the natural production of vitamin D
  • Poor absorption of vitamin D in the intestines (such as happens with 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 brittle bones and the increased risk of fractures and osteoporosis.

If you've been diligent about staying out of the sun because it tends to make your eczema worse, you may also be at risk of vitamin D deficiency. If you're concerned about your vitamin D levels, the prudent thing to do is talk to your doctor about possibly having your levels tested.

Sunlight and the Inflammatory Response

Besides vitamin D production, the sun may have other positive effects on eczema. Research has shown that exposure to sunlight may reduce inflammation of the skin, in turn improving eczema symptoms.

A 2017 study published in the Journal of Allergy and Clinical Immunology found that exposing the skin to UV light, such as sunlight, caused nitric oxide to be released into the bloodstream. Nitric oxide triggers an anti-inflammatory response in the body but activating special types of cells called regulatory T cells.

It's believed that regulatory T-cells suppress an over-reactive immune system. Because eczema is believed to be caused, in part, by an outsized reaction by the immune system it's theorized that activation of regulatory T-cells can improve the condition.

Sunlight and Eczema Prevention

What's more, some experts now believe that UV-exposure not only improves eczema, but the lack of it may be contributing to the rise in the skin condition over the last few decades. The hypothesis is that as modern society moves into a more indoor lifestyle, the lack of sunlight changes the lack of sunlight reduces the skin's barrier functions and blocks inflammatory response.

One 2019 study found that there was no difference in eczema between infants who were given vitamin D supplements as newborns and those who received none. What was discovered, though, was the infants who received less UV light exposure were more likely to have eczema.

This would suggest that UV exposure is a more important factor in preventing eczema than vitamin D supplementation. There is still much more research that needs to be done, but it is an interesting theory nonetheless.

UV Treatments (Phototherapy)

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

In this way, it works similarly to natural sunlight except in a more controlled way. This procedure can be done at your doctor's office or dermatology clinic.

Phototherapy isn't used as a first-line treatment for eczema. Instead, it is suggested when topical treatments aren't doing enough to improve the condition.

Risks of Sun (UV) Exposure

In general phototherapy, both natural sunlight and in-office UV exposure, is safe and tolerated well, but it does have some harmful effects:

  • Sunburn
  • Premature aging (lines, wrinkles, rough texture, and uneven skin tone)
  • Hyperpigmentation (dark spots or splotches on the skin)
  • Xerosis (dry skin)
  • Actinic keratosis
  • Skin cancer

The risk of developing any of these conditions increases with long-term use of phototherapy treatments. Furthermore, people with atopic dermatitis may be more prone to sunburn, especially when they are using topical steroids or Elidel/Protopic.

Sun Safety Tips

While cautious amounts of exposure to natural sunlight may be very healthy, you should take care to do so safely.

Always talk to your doctor for recommendations and advice before using sunlight as an eczema treatment.

After getting input from your doctor, keep these safety tips in mind:

  • Start with just a few minutes a day: There's no need to bake in the sun all afternoon. Don't allow your skin to burn.
  • Be aware that sunlight doesn't improve eczema in all people: In fact, for some, sun exposure can actually make eczema worse. This is because heat and sweat are eczema triggers for some people. If your eczema tends to get worse when you overheat, or during the summer months, sun therapy might not be the best choice for you.
  • Tanning salons should be avoided: Too much sun exposure puts a person at risk for skin cancer and premature aging.

Other Eczema Treatments

It's important to note that sensible sunlight exposure or vitamin D supplementation (if recommended) is simply one part of a person's eczema treatment regimen. This is because eczema care requires a holistic approach—a combination of therapies, so to speak.

With that, other eczema therapies you should discuss with your or your child's dermatologist include:

  • Behavioral modifications, for example, limiting bath time to five to ten minutes
  • Avoiding known triggers like food allergens or very dry, hot environments
  • Good skincare, for example, applying a thick cream or ointment-based moisturizer like petroleum jelly at least twice daily
  • Controlling itching by cutting fingernails short or taking an antihistamine
  • Considering eczema medication like topical steroids

A Word From Verywell

Vitamin D deficiency is a hot topic these days and has been linked to a number of other health conditions like multiple sclerosis, heart disease, diabetes mellitus, infectious diseases, and cancer. Even so, the research on its role is still being teased out, so be sure to communicate with your doctor about whether a vitamin D supplement is reasonable for you.

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  1. Thyssen JP, Zirwas MJ, Elias PM. Potential role of reduced environmental UV exposure as a driver of the current epidemic of atopic dermatitis. J Allergy Clin Immunol. 2015 Nov;136(5):1163-9. doi:10.1016/j.jaci.2015.06.042

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