Sun Allergy Q&A: What to Know Before Summertime

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There’s nothing better than the first beach day of the year. Good book and sunscreen in tow, you’re ready to enjoy a day in the sun. But a few hours or days later, you might notice an itchy red rash on your chest.

Sound familiar? It might be a sun allergy. Certain types of solar allergies affect up to 20% of the US population every year. (1) And although they usually aren’t serious, they can be uncomfortable.

We talked with Alessandro De Luca, pharmacist and medical communication expert, for his thoughts and insights. Discover the medical definition of a sun allergy, who’s at risk, and what to do about it.

Let’s get started.

What is a sun allergy?

When we sat down with Alessandro, he wanted to get one thing clear right off the bat. “The term sun allergy covers various conditions. But, when people say sun allergy or sun rash they’re usually talking about a very common condition called polymorphous light eruption or PLE.”

So, what’s the difference? Alessandro explains, “PLE is a rash that shows up on sun-exposed areas, usually during the first few times you go out in the sun (like in early spring or summer). And it’s common in lighter skin tones.”

What else do people call a sun allergy? “Solar urticaria is chronic photosensitivity, causing hives that can affect any skin tone and present on any area of the body. It’s much less common than PLE. And since they’re two different things, both could even show up at the same time.”

To sum things up, the term sun allergy is a broad one. And the most common type of sun reaction is actually a specific condition called polymorphous light eruption. That’s what we’ll focus on in this article.

What is periodic sun rash (polymorphous light eruption)?

Polymorphous light eruption is a rash caused by solar radiation in people who are sensitive to sunlight. These itchy, red, inflamed bumps or patches often pop up on the chest, forearms, lower legs, or feet a few hours to days after your first sunny outing of the season.

Not a fun way to kick off a vacation. But, the good news is that the rash usually goes away on its own within a week or two, without any scarring.

What does sun rash look like?

People with PLE typically notice that red, bumpy rash along with itching, burning, or stinging. The most affected areas are usually the ones that don’t get much sun until the summertime, like the chest or arms.

Here’s an example:

What causes a sun allergy?

Since the word sun allergy covers a lot of things, there are a variety of causes. Some people have a type of sun allergy that’s passed down through genetics. Others have specific triggers — such as certain medications or even contact with plants. And many of the causes behind sun reactions are still being studied.

Common sun rash or PLE is thought to be caused by your body’s immune response to sunlight after a long period of staying out of the sun. Alessandro elaborates, “This common type of sun allergy often shows up in women, starting in your teens or 20s. After the first rash, recurring episodes might happen year after year.”

Who’s at risk for a sun allergy?

Depending on the type of sun allergy, the condition can affect all genders, ages, and skin tones. But polymorphic light eruption makes up about 70% of all skin reactions from the sun. (Source) And this type of sun rash often appears in younger women who live in four-season climates.

Normally the reaction appears a few hours after first being exposed to the sun. Especially as your skin “gets used to it”, the reaction decreases, making outbreaks in the middle of summer less common.

Here are a few factors that can make experiencing a seasonal sun rash (PLE) more likely:

• Having a light skin tone that sunburns easily
• Living in northern regions that don’t get much winter sun
• A family history of sun reactions
• Being a female

How can you help treat a sun allergy?

First things first, get your dermatologist involved. “Remember that sun allergy is an umbrella term, and your dermatologist will be able to best diagnose the type and advise treatment,” advises Alessandro.

When it comes to PLE or periodic sun rash, it’s best to get your first rays gradually to help minimize symptoms. Take your time, you’ve got all summer! And always use sun protection: including proper sunscreen application, protective clothing, and seeking shade during peak sun hours.

Just the FAQs

Is a sun allergy an autoimmune disease?

Again, there a many types of sun allergies. The most common sun reaction, polymorphic light eruption, can be considered an autoimmune response to UV exposure. (Source)

People with PLE have immune cells that are triggered by UV rays. And these cells create a defense response in the skin, causing an unpleasant rash.

Is a sun allergy serious?

While periodic sun rash (or PLE) usually clears up quickly on its own, it’s always a good idea to check in with your dermatologist about any skin concern.

Here’s when you should seek immediate medical care:

• Your rash is spreading quickly or already widespread
• Your rash is painful
• You also have a fever

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Now you know more about your skin, sun allergies, and the most common type of sun reaction: polymorphic light eruption. And since you’re into keeping your skin healthy, we’ll leave you with two tips: remember to use broad spectrum sunscreen daily and check in with your dermatologist regularly.

Above all, love your skin, care for it, and protect it, always.

Reference:
1 Frcpc, S. a. a. M. (n.d.). Polymorphous Light Eruption: Background, Pathophysiology, Etiology. https://emedicine.medscape.com/article/1119686-overview 
2 Gruber-Wackernagel, A., Schug, T., Graier, T., Legat, F. J., Rinner, H., Hofer, A., Quehenberger, F., & Wolf, P. (2021). Long-Term Course of Polymorphic Light Eruption: A Registry Analysis. Frontiers in Medicine, 8. https://doi.org/10.3389/fmed.2021.694281 
3 Harris, B. W. (2022, September 27). Solar Urticaria. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK441986/ 
4 Oakley, A. M. (2022, August 8). Polymorphic Light Eruption. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK430886/