Shingles at 38
When you have eliminated the impossible, whatever remains, however improbable, must be the truth.
-Arthur Conan Doyle
Something was off.
Two days of itching on my upper left back and left thigh. A sore foot, no fever, and red dots. Nothing dramatic.
I opened Claude and typed:
“I’m itchy on my upper left back and left thigh. They’ve been itchy for two days. Neither are red at all. They both hurt a bit and feel itchy. I haven’t been scratching at all. There are now red dots on my leg, and my left foot feels sore too. What could it be?”
It flagged five possibilities: contact dermatitis, shingles, folliculitis, insect bites, or an allergic reaction. I went through each possibility, learning the symptoms and causes. Through the process of elimination, only shingles remained.
This was weird because I’m in my late 30’s. Shingles is supposed to be a disease of grandparents. The shingles vaccine is only recommended for people over 50. Current guidance says you should only get the vaccine before 50 if you have a weakened immune system, which I don’t.
But the model was clear: one-sided, painful, spreading along a dermatome. As soon as blisters appear, there’s a 72-hour window to take antivirals to slow the spread.
So I kept asking.
“How is onset defined for shingles?”
“It’s only red now, no blisters. So is that before onset?”
“What are the symptoms of someone with shingles?”
By the end of the conversation, I had a working hypothesis, a sense of what to watch for, and the language I needed to walk into a doctor’s office with conviction. I couldn’t see my doctor in person, so I booked a virtual visit the next day.
The doctor was unsure. There were no blisters yet, just the prodromal pain and a faint redness. Diagnosing shingles without a rash is a coin flip; there’s no fast blood test for it. But valacyclovir is cheap, the side effects are benign, and the cost of being wrong is a week of unnecessary pills. The cost of being right and waiting is permanent nerve damage. He wrote the prescription.
Later that day, the blisters came in exactly where the model said they would. By then, I had already taken my first antiviral. Shingles still wasn’t fun, but I had a milder version than I would have had.
What this is, and what it isn’t
The LLM didn’t write the prescription or take responsibility for the decision. It generated a hypothesis fast enough that I could carry it into a real appointment before the treatment window closed. The doctor still made the call.
Understanding that it was likely shingles led me to meet with my doctor. A past version of me would have Googled “itchy red dots leg” and gotten ten web pages of contact dermatitis.
The standard pipeline (notice symptoms, make an appointment, wait 3 days, describe symptoms in 90 seconds, get a guess) is too slow for illnesses like shingles.
How to actually do this
Describe what you actually feel, not what you think it is. My first prompt was a mess of contradictory observations (”red spots... neither are red at all”). The model worked with it anyway. Be specific. Side, timing, character of pain, what has changed today and over time.
Ask follow-ups until the differential narrows. The first answer is rarely the answer. Iterate, ask again in different ways in new threads. Then ask about onset, treatment windows, and what symptoms would look like next. Each question prunes the tree.
Bring the conversation to your doctor as your own framework. Not “the AI said,” but “I’m worried about X because of Y and Z, can we rule it out?” Doctors respond to specific hypotheses much better than they respond to “I feel weird.”
Shingles
I know more than half a dozen friends who have had shingles in their twenties or thirties. All healthy men who work similarly intense jobs as me. For many of them, it was the worst pain they’ve ever had. I only learned they had it before when I told them I had it. None of them fit the textbook profile.
The textbook says shingles is for the elderly and the immunocompromised. The textbook is being outpaced by what’s actually showing up in clinics.
There’s also a pattern of these cases in men after the COVID vaccination. The mechanism is plausible (transient changes in cell-mediated immunity can theoretically reactivate latent varicella zoster).
The window closes fast
Antivirals don’t cure shingles. They shorten it and, more importantly, reduce the risk of PHN– nerve pain that lasts months or years after the rash is gone. I have mild PHN. It acts up when my workload gets particularly high. It’s like a spidey-sense, except it comes from my left leg.
If something feels off, have the first conversation with an LLM, and the second with a doctor.