This was not normal for a sunburn. what is wrong?

The woman shouted to her 80-year-old husband, “Come sun.” “You’re turning red!” The man reluctantly walked toward the house. It was late afternoon—the end of a glorious summer day in Orange, Connecticut. But when he looked at his exposed arms, he could see that she was right. It was bright pink, he soon knew his arms and the back of his neck was probably red and itchy. It’s time to get in.

He suspected that it gave his wife some kind of coolness to suddenly become as sensitive to the sun as ever. He loved the sun and until recently thought it was loving him back, which made olive skin a dark brown which seemed to him a sign of health. But that spring it began to redden wherever the sun hit it. It wasn’t exactly a sunburn, or at least not the kind of burn his wife used to get that made her skin turn red, peel, and ache for days.

His sunburn was itchy, wasn’t painful, and lasted an hour or two, sometimes a little more. It certainly didn’t last long enough to be seen by a dermatologist, Dr. Jeffrey M. Cohen. He told his doctor about the rash that spring when he went for his annual skin exam. Cohen said he might be allergic to the sun and suggested an antihistamine and strong sunscreen. He took the pills when he thought about it and put on sunscreen a while, but he wasn’t sure it did much. Besides, who has ever heard of sun allergies?

He made an appointment with his dermatologist just before Christmas. It was one of those warm, sunny days in December, before winter really comes around, so he decided to make sure his doctor had a chance to see the rash. Arrived early and parked in the parking lot. He took off his jacket and stood in the sunlight that faintly streamed onto the building. After about 10 minutes he saw that it had turned pink, so he headed to the office.

“I have something to show you,” he told Cohen with a smile as the doctor entered the brightly lit examination room. He unbuttoned his shirt to reveal his chest. It was now bright red. The only places on his torso that appeared to be his natural color were those that had been covered with a double layer of fabric—the tape under the shirt buttons, the points of the collar, and the double folds of fabric on his shoulders. Bali was the area below his left chest pocket where his cell phone was.

Cohen was amazed. Obviously, this was not a sunburn. For Cohen, it looked like a classic symptom of what’s called photodermatitis — an inflammatory skin reaction caused by sunlight. Most of these unusual rashes fall into one of two categories. The first is a phototoxic reaction, often seen with certain antibiotics such as tetracycline. When someone takes these medications, the sun can cause an immediate, painful rash that looks like a sunburn and can last for days, like a regular sunburn, causing blistering and even scarring. This patient apparently had an immediate reaction to sunlight, but he insisted that the rash didn’t hurt. It just itches like crazy. And it was gone within hours. His reaction was more like photoallergic dermatitis, in which sunlight causes hives—raised, red spots that itch intensely and last less than 24 hours. But this was not suitable either; Photoallergic reactions are not immediate. They usually take a day or two to appear after exposure to light.

Each reaction is stimulated by drugs. Cohen reviewed the patient’s comprehensive medication list. Amlodipine, an antihypertensive drug, is known to cause this type of photosensitivity, but the patient started this drug recently, months after the rash was first mentioned. Hydrochlorothiazide, another blood pressure medication, can sometimes do this. The patient had taken this drug for years and was fine, but at least in theory, this unusual type of reaction could start at any time.

Cohen explained his reasoning to the patient. A biopsy will need to be taken to confirm the diagnosis. Pathology will help him distinguish urticaria from more destructive phototoxic reactions that destroy skin cells. This will help him rule out other possibilities such as systemic lupus erythematosus, an autoimmune disease that is more common in middle-aged women but can occur in men and women of any age.

Two days later, Cohen received his answer. It was hives – known medically as urticaria. This was a photoreaction. It may have been caused by hydrochlorothiazide. Cohen told his patient he should ask his primary care physician to stop the medication, and after a few weeks he should stop getting the rash.

The man returned to Cohen’s office three months later. The rash has not changed. After a few minutes in the sun it will feel itchy and pink, even in the gloom of winter. Cohen is back on the medical patient list. None of the others have been linked to this type of reaction. He said, “Tell me about that rash again.” The patient reviewed his story again. Anytime the sun hits his skin, even if the sun was coming through a window, he would turn red. When he was driving, the warm touch of the sun on his arm was very itchy. By the time he reached his destination, his skin would be bright red. Upon hearing this description, Cohen suddenly realized he was right the first time. The patient developed an allergy to sunlight – a condition known as solar urticaria.

Cohen explained that this was not a sunburn. Sunburn is caused by light with shorter wavelengths known as ultraviolet B or UVB rays. This form of light cannot penetrate glass. The fact that he was able to get that redness through his window suggests that his reaction was triggered by longer wavelength light, known as UVA. This is the form of light that causes the skin to tan and age, and it is the form used in tanning salons.

He explained that solar urticaria is a rare and poorly understood disorder. When the sun’s rays penetrate the skin, they interact in different ways with different cells. The most common are those cells that, when exposed, produce a pigment known as melanin, which tans the skin and provides some protection from the other effects of the sun. In people with solar urticaria, the body has an immediate allergic reaction to a component of the cells that has been altered by sunlight. How and why this change occurs is still unknown. Allergies can start in adolescence and may last a lifetime. It is difficult to treat.

Cohen told him sunscreen is a must—even indoors. He’ll also need to take a higher dose of the antihistamine he’s been prescribed – at least double the usual recommended dose. Patients are also advised to wear protective clothing. Solar urticaria can be dangerous. Extensive exposure to sunlight can lead to severe reactions, and rarely to fatal anaphylaxis.

The patient received the diagnosis a little over a year ago and has been using a sunscreen with SPF 50 ever since. Double the dose of antihistamines. And most of the time, medication plus long pants, sleeves, and a hat keep him safe. Most of the time. And when he does forget, he knows he can count on his wife to let him know he’s starting to turn red again.

Lisa Sanders is a contributing writer for the magazine. Her most recent book is Diagnosis: Solving Medical’s Most Perplexing Mysteries. If you have a resolved case you want to share, write to [email protected].