“Get out in the sun,” the woman shouted to her 80-year-old husband. “You’re turning red!” It was late afternoon at the end of a glorious summer day in Orange, Connecticut. But when he looked down at her exposed arm, it turned out she was right. He’s bright pink and you’ll soon see his arms and probably the back of his neck will be red and itchy. It’s time to go inside.
He suspected that his wife’s sudden sensitivity to the sun had made her feel some kind of excitement. He loves the sun and until recently he thought the sun loved the sun. His olive skin turned dark brown, which seemed to be a sign of his health. But that spring, wherever the sun hit him, he began to turn red. It wasn’t exactly a sunburn, but at least it wasn’t the kind of burn that his wife had once suffered, reddening, peeling, and painful for days.
His sunburn was non-itchy, painless, and lasted an hour or two, sometimes longer. It certainly didn’t last long enough for his dermatologist, Dr. Jeffrey M. Cohen, to observe it. He told his doctor about the rash that spring when he went for his annual skin exam. Cohen said he could be allergic to the sun, and he recommended an antihistamine and strong sunscreen. He took the pills on a whim and applied sunscreen every once in a while, but he wasn’t convinced it would do much. And who ever heard you’re allergic to the sun?
definitely not a sunburn
He made an appointment with a dermatologist just before Christmas. It was one of those warm, sunny days in December before winter really set in, so he decided to see if there was an opportunity to see a doctor for the rash. He arrived early and parked in the parking lot. He took off his jacket and stood in the weak sunlight that fell on the building. About ten minutes later, he found his skin turning pink, so he headed to his office.
“I have something to show you,” Dr. Cohen said with a smile as the doctor entered the brightly lit examination room. He unbuttoned his shirt to expose his chest. It’s already bright red. The only places on his torso that appeared to be of normal color were those covered with a double layer of fabric – the placket strip under the shirt button, the tip of the collar, the double fold of fabric over the shoulder. The palest part was under his left breast pocket, where his cell phone had been.
Cohen was astonished. This was clearly not a tan. For Cohen, it looked like the classic symptom of so-called photodermatitis, an inflammatory skin reaction caused by sunlight. Most of these unusual rashes fall into one of two classes. The first is a phototoxic reaction, commonly seen with certain antibiotics such as tetracycline. When these drugs are taken, the sun can cause a painful sunburn-like rash to occur immediately, which, like a normal sunburn, can last several days and cause blisters and scarring. Apparently, this patient had an immediate reaction to sunlight, but claimed that the rash was painless. I was itching like crazy. And within hours it was gone. His reaction resembled photoallergic dermatitis, where sunlight causes hives. Urticaria is a raised red patch with intense itching, the duration of which he less than 24 hours. But it didn’t quite fit either. Photoallergic reactions do not appear immediately. It usually takes a day or two from exposure to light to erupt.
Each reaction is caused by a drug. Cohen reviewed an extensive medical list of patients. The antihypertensive drug amlodipine was known to cause this type of photosensitivity, but the patient recently started taking the drug, months after he first mentioned the rash. His other blood pressure medication, hydrochlorothiazide, can sometimes cause this. The patient had been on the drug for years and was doing well, but in theory at least this unusual type of reaction could start at any time.
Mr. Cohen explained his thoughts to the patient. A biopsy may be needed to confirm the diagnosis. This pathology may help distinguish between the inflammation of urticaria and the more destructive phototoxic reaction that destroys skin cells. And that would help rule out other possibilities, such as systemic lupus erythematosus, an autoimmune disease that is most common in middle-aged women but can occur in men and women of all ages.
A few days later, Cohen found the answer. It was hives, medically known as hives. This was a photoallergic reaction. And it’s probably caused by his hydrochlorothiazide. Dr. Cohen told patients that they should ask their doctor to stop taking the drug and tell them the rash should go away in a few weeks.
through the window
The man returned to Cohen’s office three months later. His rash remained unchanged. After a few minutes of exposure to the sun, it becomes itchy and pink, even in the middle of winter. Cohen is back on the patient’s medical list. None of the others were related to this kind of reaction. “Tell me about this rash again,” he said. The patient repeated his story again. When the sun hit his skin, he turned red, even though the sun was shining through the window. When he was driving his car, the itching got worse when the warm sun hit his arm. And by the time he reaches his destination, his skin will be bright red. After hearing this explanation, Cohen suddenly realized for the first time that he was right. The patient had developed an allergy to sunlight, a condition known as solar urticaria.
Cohen explained that this is not a tan. Sunburn is caused by short wavelengths of light known as ultraviolet B or UVB. Light in that form cannot pass through the glass. The fact that he turned red through the window indicates that his reaction was caused by his longer wavelength light known as UVA. This is the form of light that tans and ages the skin and is the form used in tanning salons.
He explained that solar urticaria is a rare and poorly understood disease. When sunlight penetrates the skin, it interacts with different cells in different ways. The best known are the cells that produce a pigment known as melanin upon exposure, which tans the skin and provides some protection from other effects of the sun. People with solar urticaria develop an immediate allergic reaction to one of the cellular components altered by sunlight. It is not yet known how or why this change occurs. Allergies begin in adulthood and may be lifelong. and difficult to treat.
Cohen says sunscreen is a must, even if you’re indoors. They also need to take higher doses of prescribed antihistamines (at least twice the usual recommended dose). Patients are also advised to wear protective clothing. Solar urticaria can be dangerous. Prolonged exposure to sunlight can cause severe reactions and, in rare cases, fatal anaphylaxis.
The patient was diagnosed about a year ago and has been using SPF50 sunscreen ever since. He doubled his antihistamine dose. And most of the time, medicine, long pants, long sleeves and a hat keep him safe. most of the time. And when he forgets, he knows he’ll let his wife know that he’s starting to turn red again.
Lisa Saunders, M.D., is a contributor to this journal. Her most recent book is Diagnosis: Solving the Most Baffling Medical Mysteries. If you would like to share a resolved case, please email [email protected].
