When the Sun Becomes a Trigger: EDS, Skin Flares, and the Spring Transition

Geeta BihariFounder, Rebuilt With Geeta · EDS · rebuiltwithgeeta.com

I thought I was allergic to the Caribbean.

Two years in a row — February one year, April the following spring break — I traveled from a New England winter to the Caribbean. And two years in a row, within days of arriving, I developed an intensely itchy rash spreading across my skin.

Two consecutive trips. Same destination. Same reaction. The logic was airtight: I was clearly allergic to the Caribbean.

I went through the list of obvious suspects — a plant, the ocean, the hotel detergent, something I ate. Nothing added up. I joked to anyone who would listen that I was apparently allergic to paradise.

A dermatologist eventually explained what was actually happening. The diagnosis was Polymorphic Light Eruption (PMLE) — commonly referred to as a sun allergy, though that framing undersells what’s actually occurring. My immune system wasn’t reacting to the Caribbean. It was reacting to the abrupt and dramatic change in ultraviolet exposure.

Think about what my body had been through. For months, my skin was covered by winter clothing. I was living through short days, weak sunlight, and temperatures in the 20s and 30s. Then, in less than 24 hours, I was standing in 85-degree tropical sunshine. My immune system interpreted that shift as a threat and responded accordingly. Two years in a row. Same pattern. Same body. Same New England winter. That’s when it finally made sense.

The itching started first. The rash — technically urticaria — followed two to three days after the initial exposure. PMLE typically has that delayed presentation, which makes it harder to connect the dots in the moment. By the time the rash appears, people have often forgotten about the sun exposure that triggered it.

Why this happens more in EDS, MCAS, and autoimmune conditions.

PMLE is not exclusive to people with EDS or immune dysregulation — it affects a meaningful portion of the general population, particularly in northern climates where winter sun exposure is minimal. But for people already managing a reactive immune system, the spring transition can be particularly pronounced.

EDS and MCAS frequently co-occur. Mast cells — the immune cells found throughout connective tissue, skin, and mucous membranes — are already primed to respond to environmental triggers in people with MCAS. UV exposure is one of those triggers. So is heat. So is the rapid temperature change that comes with spring. For someone whose mast cells are already hyperreactive, the combination of more sunlight, warmer temperatures, and increased time outdoors can push the immune system into overdrive in ways that feel sudden and confusing.

At the same time, every spring I see an increase in posts about malar rashes — the butterfly-shaped rash across the cheeks and nose — in the EDS and chronic illness community. Some of these may be lupus-related photosensitivity. Some may be rosacea triggered by temperature change. Some may be MCAS skin reactions. Some may be PMLE. They can look remarkably similar. Understanding which one you are dealing with changes the management approach entirely.

There is an important subset of contact dermatitis worth understanding separately: photocontact dermatitis. This occurs when certain chemicals on the skin — including ingredients found in sunscreens and cosmetics — become reactive specifically when exposed to UV light. The sun activates the chemical, and the chemical then triggers the skin reaction. This is why some people find that sunscreen worsens their reactions rather than helping — the product itself is not the issue until UV light enters the equation.

A note on lupus and photosensitivity.

For people with lupus, sun exposure is not simply a trigger for a skin rash. UV light can activate a systemic immune response that goes well beyond the skin — triggering joint pain, fatigue, and broader disease flares. Photosensitivity is one of the diagnostic criteria for lupus and needs to be taken seriously as part of overall disease management.

Hydroxychloroquine is a cornerstone medication for many people with lupus. It works by reducing the immune system’s sensitivity to UV light and modulating the inflammatory response. It is typically taken continuously under physician supervision — it is not a seasonal medication to start and stop. If you have lupus and are concerned about sun sensitivity, this is a conversation to have with your rheumatologist, not something to manage on your own.

If you are seeing a malar rash for the first time — or a rash pattern that is new to you — please see a physician before drawing conclusions about what it is. Lupus is one possibility. It is also not the only one. Getting the right diagnosis matters.

What I learned about sunscreen — and why I stopped using it.

This section will probably surprise some people.

When my skin was reacting, the standard recommendation was to use sunscreen. Every doctor said it. Use sunscreen. I tried. And in my case, sunscreen consistently made things worse. I kept going back. I kept hearing the same advice. Until one dermatologist finally said something different: just stop.

That advice turned out to be the most useful thing anyone told me. Here is why it worked.

The chemical ingredients in many conventional sunscreens — and in cosmetics, fragrances, and skincare products more broadly — can themselves become reactive when exposed to UV light. This is called photocontact dermatitis. The UV exposure activates the chemical on your skin, and the chemical then triggers the reaction. For skin that is already sensitized, you are not adding protection — you are adding a trigger. The sunscreen was making my immune response worse, not better, because the chemicals were reacting with the very UV light I was trying to block.

I want to be clear: I am not recommending that people stop using sunscreen. Sun protection is genuinely important, particularly for people with lupus, a history of skin cancer, or significant photosensitivity. What I am sharing is that for me — and for many people with sensitive or reactive skin — the chemical load of conventional sunscreen was contributing to the problem. Simplifying my routine dramatically reduced my reactivity.

If you suspect your skincare products may be contributing to skin reactions, the EWG Skin Deep database is a useful resource for identifying products with lower chemical loads. I moved to EWG-approved or certified products and eliminated most of my routine entirely. I wear no makeup. I choose cotton clothing and UV-protective shirts over topical sun protection where possible.

The approach that actually worked for me.

After my Caribbean experience, I did not avoid the sun. I did the opposite — carefully and deliberately.

The principle is gradual desensitisation. My skin had been sun-deprived through a New England winter. The solution was not to protect it from all UV exposure indefinitely. It was to slowly reintroduce UV exposure so my immune system could adapt without being overwhelmed.

• 01
  Expose throughout winter — not just springEven short periods of outdoor exposure during winter months — a few minutes at a time — prevent the complete UV deprivation that makes the spring transition so dramatic. I now make a point of getting some outdoor light exposure year-round, even on cold days.
• 02
  Increase exposure gradually in springRather than spending hours outdoors as soon as warm weather arrives, I build up slowly. A few minutes. Then a little more. The goal is to give the immune system time to adapt to increasing UV levels without triggering a threshold response.
• 03
  Simplify your product routineRemove as many variables as possible. If you are experiencing skin reactions, fewer products means fewer potential triggers. Start with the simplest possible routine and add back carefully, one product at a time, noting any responses.
• 04
  Choose physical protection over chemicalUV-protective clothing, wide-brimmed hats, and shade are effective and carry no chemical load. For people with reactive skin, physical barriers are often better tolerated than topical products.
• 05
  Become a pattern detectiveTrack what happened, when, what changed, what products were used, how much sun exposure occurred, and what season it is. Skin reactions have patterns. Identifying those patterns — and bringing them documented to your dermatologist — is the most useful thing you can do.
• 06
  Work with a dermatologistPMLE, MCAS reactions, eczema, and contact dermatitis all look similar and require different approaches. A dermatologist can help identify which type of reaction you are dealing with and guide appropriate treatment. Topical corticosteroids — such as triamcinolone acetonide — are commonly prescribed for dermatitis and can be helpful when used under medical supervision.

The deeper lesson.

My skin journey taught me something that extends well beyond rashes and sun exposure.

The body is not an enemy. It is a system with patterns. And those patterns, once you learn to read them, become information rather than chaos.

When I stopped fighting my skin reactions and started asking what they were trying to tell me — what changed, what triggered this, what made it better — I stopped feeling like my body was randomly attacking me and started feeling like I was working with it.

That shift in perspective is one I have returned to again and again across every aspect of managing EDS. The symptoms are not betrayal. They are communication. The work is learning the language.