Sun Exposure, Phototherapy, and Psoriasis: What You Should Know

Phototherapy can be an effective strategy for psoriasis management, but it’s important to understand the potential risks of excess sun exposure.

If you have psoriasis (PsO), you know your symptoms can be better at certain times and worse at others.

Flares may happen randomly, but it may also seem that they happen more frequently during cold weather and less during the warmer months when you spend more time in the sun.

Although aspects of PsO are poorly understood, what we do know is that it’s an autoimmune condition where the growth cycle of skin cells is faster than normal, causing skin cells to shed too early. This leaves behind patches, known as PsO plaques, of localized inflammation and an overproduction of cells.

There is some evidence that exposure to UV rays plays a role in developing these plaques, but it’s also important to recognize the risks of sun exposure.

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The sun emits UV rays in two forms

UVA

UVA makes up more of the sun’s rays. These are the longer rays, and the rays mostly responsible for the tanning of skin. (Tanning beds have more of this type of ray.)

UVA requires the skin to be sensitized by a plant-derived chemical called psoralen before it’s effective for treating PsO. This treatment is called PUVA (aka Psoralen plus UVA rays).

UVB

UVB rays are shorter rays that make up less of the sun’s rays but are responsible for sunburns. UVB rays can slow the growth of skin, decrease scaling and inflammation, and also help your body make vitamin D.

To be most effective for treating PsO plaques — while avoiding sunburns or skin damage — UVB ray exposure needs to be spread out over time.

How does ultraviolet therapy for plaques work?

An effective way of managing PsO plaques is with exposure to ultraviolet (UV) rays. This is possible with natural sunlight or indoor phototherapy, but in most cases, phototherapy is preferred.

Exposure to UV rays stops the overproduction of skin cells by damaging, or locking in, their DNA. This essentially stops the cells from reproducing, which in turn stops the entire process behind plaque formation.

What are the clinical benefits of phototherapy?

Phototherapy is a form of medically administered UV rays. This is used to treat PsO along with a few other conditions, including eczema, newborn jaundice, and vitiligo.

Phototherapy is preferred over direct sun exposure, as a healthcare professional can control the strength of light and how long you’re exposed.

The downside is that this type of treatment can be expensive, inaccessible, or unavailable for some people. In those cases, your doctor may be able to suggest ways to manage natural sunlight exposure safely in order to see benefits.

Clinical improvement of PsO plaques is notable following UV ray exposure, in either natural sun or with phototherapy. Small amounts of UV rays reduce both local and systemic inflammatory markers.

Most people with PsO have fewer scales and patches during the summer months and when living in warmer, sunnier climates.

What are the challenges of UV therapy?

The tricky part of UV exposure for treating PsO is that there is no way to be sure how much UV ray exposure is enough or how long the improvements will last.

Some people have complete resolution after a handful of treatments, and some need to continue for an extended period of time. Overall, PsO is poorly understood in many ways, making this complex treatment more challenging.

Any exposure to UV rays can also cause skin cancer, so this treatment increases cancer risk.

This treatment also increases the risk of sunburns by causing trauma to the skin, which may trigger the Koebner phenomenon. This phenomenon is when skin that did not previously have PsO plaques suffers a trauma and the affected area begins to present with plaques.

Too much UV ray exposure can actually worsen PsO and the appearance of plaques over time.

Because of these risks, UV exposure treatments are considered a second-line treatment, which means this is only recommended by a healthcare professional after topical creams, ointments, and other emollients have been ineffective.

Tips for safe sun exposure

When it comes to UV exposure and PsO, here are some tips to help keep you and your skin as safe as possible:

• Stay hydrated! Keeping yourself and your skin hydrated is the easiest way to maintain healthy skin.
• Wear a hat whenever possible.
• Spend time outdoors before 10 a.m. or after 3 p.m. to avoid the hottest parts of the day.
• Never intentionally stay in direct sunlight for any period of time.
• Wear eye protection when outdoors or receiving phototherapy treatments.
• Never fall asleep in the sun.
• Wear sunscreen for any prolonged period outdoors. Be sure to opt for a waterproof and sweatproof option whenever possible.
• Avoid sunburns by starting with very short sun exposure — think 5–10 minutes at a time.
• Moisturize every day, especially before and after sun exposure. If you spend a lot of time in the sun during the day, opt for a moisturizer with sunscreen in it.
• If you do sunburn, use oatmeal, aloe, and other moisturizers to help the skin heal. If you develop blisters, do not pop them.
• Check your medications, as some may cause photosensitivity. This means you may be more sensitive to the sun’s rays, which can make you more prone to sunburns. (Your doctor or a pharmacist can help you check your prescriptions.)
• Protect your feet, too! The tops and bottoms of your feet can burn quickly in some environments.

The takeaway

UV rays can help control PsO and the plaques that come with it, but more information is needed to determine safe limits of this exposure.

If you want to learn more about phototherapy, reach out to a healthcare professional to see if this treatment is an option for your psoriasis treatment plan.