A sun allergy can feel as if it comes out of nowhere. You spend an afternoon outside, then notice itching, bumps, hives, dryness, or a burning rash across your chest, arms, or face.
You may think you touched something you were allergic to. Or maybe it came from a bug bite? You can’t remember this happening when you were younger. So what’s going on?
The answer may be more complicated than you think. Your skin can become unusually sensitive to sunlight, sometimes because of an immune reaction and sometimes because the sun is interacting with a medication or product on your skin.
Might this be what’s going on?
Let’s look more closely at what a sun allergy is, and if you have it, what you can do to protect your skin and help it recover more quickly.
Q: Do you get a rash or break out in itchy bumps after a day in the sun?
Tip: Use gentle, unscented, anti-inflammatory, barrier-strengthening moisturizers like those from CV Skinlabs to help combat skin dryness, calm redness and itching, and soothe and repair a compromised skin barrier.
What Is a Sun Allergy?
“Sun allergy” is a general name for several skin reactions triggered by sunlight. It doesn’t always mean you’re allergic to the sun itself.
The most common type of sun allergy is polymorphic light eruption, or PMLE. It usually shows up in spring or early summer. Your skin has been covered for months, and then suddenly it’s exposed to stronger ultraviolet light.
PMLE can cause itchy bumps, raised patches, tiny blisters, or burning areas several hours to a few days after exposure. It usually affects the upper chest, arms, hands, legs, or other areas that have recently been uncovered.
Research suggests that PMLE may effect 10 to 20 percent of the population. A 2023 study of 844 patients found that most were women and that the average age when symptoms started was about 42. That shows us that this type of allergy can develop later in life, even if you never saw any signs of it before.
Scientists don’t yet know the exact cause of PMLE. The leading theory is that UV light changes or creates a substance within the skin. The immune system then mistakes that substance for a threat and launches an inflammatory reaction. Typically, UV light helps quiet immune activity in the skin. But that natural response may not work as it should in people with PMLE. Factors like genetics, oxidative stress, and sudden increases in sun exposure may all affect who develops it and when the symptoms may first show up.
Other forms of sun sensitivity include:
- Solar urticaria: Sunlight causes hives, usually within minutes.
- Phototoxic reactions: A medication or skin product makes UV damage occur more easily, creating a strong sunburn-like reaction.
- Photoallergic reactions: UV light changes a substance in or on the skin, and the immune system then reacts, causing an itchy, eczema-like rash.
- Skin compromised post-chemotherapy may have an increased sensitivity to sunlight, leading to severe sunburns, rashes or other skin issues.
What Does a Sun Allergy Look Like?
A sun allergy rash usually shows up on areas that were exposed to the sun. It may itch, sting, and swell up, and it may cause bumps, hives, and small blisters, as well as dryness.
The color varies depending on your skin tone. The rash may look pink or red on lighter skin, or purple, brown, or gray on deeper skin tones.
When did the rash show up? This can offer an important clue.
Hives that rise within minutes of sun exposure may point to solar urticaria. A bumpy, itchy rash that appears several hours or days later may be PMLE. A severe sunburn or eczema-like rash after starting a medication or new product may be a photosensitivity reaction.
It’s often a good idea to see a dermatologist. They can examine the rash and help diagnose it, which can be helpful as sunburn, heat rash, eczema, contact dermatitis, and autoimmune conditions can sometimes look similar.
Why Can a Sun Allergy Suddenly Appear?
Scientists still aren’t sure why you can go much of your life without having any reaction to the sun, then suddenly start struggling with it.
In PMLE, UV light seems to change substances or proteins in the skin. The immune system can then mistake those for a threat and cause inflammation.
Research also suggests that oxidative stress can play a part. Unstable molecules called free radicals typically multiply after UV exposure, and they can cause cell damage. A review of PMLE research describes how this can lead to PMLE.
Your first reaction may occur after a larger dose of UV light than usual. So that first weekend at the beach after a long winter, or an afternoon gardening for several hours. Spending time at a higher elevation on a warm, sunny day may be enough to trigger the reaction.
PMLE sometimes becomes less severe as the summer goes on because over time, repeated small exposures can make the skin less reactive. Doctors sometimes call this the “hardening” effect. One long-term study of PMLE found that repeated sunlight exposure may reduce symptoms for some people, though the rash may also return after months with little exposure.
This doesn’t mean that tanning is a safe treatment, though. UV light can still cause premature aging and skin damage that can lead to cancer, so it’s important to be careful.
Sun Allergy Triggers You May Not Expect
Many times, the reaction comes from something you have on the skin that then reacts with the sun and causes the problem. Some possible triggers include the following:
- Medications: Some antibiotics, anti-inflammatory medications, water pills, acne treatments, and other drugs can increase sun sensitivity. A 2022 review of drug-induced photosensitivity explained how medications can cause allergic reactions. Ask your doctor or pharmacist whether anything you’re taking may have photosensitivity as a side effect.
- Products: Fragrances, topical medicines, and some cosmetics can also react with sunlight. Alpha hydroxy acids (AHAs), for example, can also increase the chance of a sunburn, which can lead to a sun rash.
- Autoimmune diseases: Some of these can cause photosensitive rashes.
When a rash is new, think back over the previous few weeks. Did you start using a prescription exfoliating acid, retinoid, perfume, essential oils, or new sunscreen? If you keep close track for a few weeks, you may be able to determine your triggers.
How to Prevent a Sun Allergy Reaction
The best approach is prevention, so start by avoiding the sun, particularly during intense UV exposure times, usually between the hours of 10:00 a.m. and 3:00 p.m. Use a broad-spectrum, water-resistant sunscreen with SPF 30 or higher every day. For sensitive skin, look for fragrance-free mineral sunscreens made with zinc oxide, titanium dioxide, or both.
Add shade, a wide-brimmed hat, sunglasses, and tightly woven or UPF-rated clothing. Increase your outdoor time gradually between winter and spring.
Finally, keep a simple reaction diary. Record your time in the sun, products used, medications taken, plants or foods touched, and how quickly the rash appeared. Having data like that can help you and your dermatologist figure out what’s going on and how to reduce your triggers.
How to Calm Skin After a Sun Allergy Reaction
Start by getting out of the sun. Cool your skin with a clean, cool compress. Avoid putting ice directly on the skin, as that can cause more damage.
Skip scrubs, acids, retinoids, fragrance, hot water, and heavy makeup until the skin settles.
For cooling hydration, mist irritated areas with our award-winning Rescue + Relief Spray. It was created to soothe and hydrate dry, flushed, itching, or burning skin, including skin irritated by sun exposure. Year after year, it’s voted best after-sun skin soother and best skin relief.
Once the skin has cooled down, apply Calming Moisture to the face, neck, or scalp. For larger areas of the body, try our Body Repair Lotion. Both provide gentle moisture without any synthetic fragrance. These moisturizers will also help repair a compromised skin barrier while improving skin health and radiance.
On very dry, unbroken patches, a thin layer of Restorative Skin Balm can help seal in moisture and support the skin barrier. Wait until the heat has left the skin before applying the balm so that you don’t trap it inside.
These products can provide nourishing and healing after-care, but if the rash doesn’t improve, be sure to see a dermatologist. And if you experience more serious symptoms like trouble breathing, faintness, or significant swelling, talk to your doctor right away.
Do you have a sun allergy?
Featured image by Dija Martins via Pexels.