Between tick and decay: a cultural history of self-diagnosis

It always begins harmlessly.

A slight twitch in the left eyelid, eight in the evening, the phone is in your hand anyway. You type “eyelid twitching”. Google delivers 42 million hits. In first place is magnesium deficiency — that would be the sensible version of the story, but who reads first place. By 8.15 p.m. you are at multiple sclerosis. By 8.40 p.m. at amyotrophic lateral sclerosis. By 9.30 p.m. on a website consisting solely of capital letters and a donate button.

At 8.30 the next morning this person is standing in your pharmacy, with dark rings under both eyes, one of which is still twitching, saying the sentence that unites every pharmacy in the country: “I know you’re going to laugh, but I read something.”

No. We are not laughing. We have all heard it before.

The typology

The man with the printout. He never comes with a question, he comes with evidence. Fourteen pages, double-sided, marked with highlighter, including at least one forum post from 2011 and a study on six rats. He has not read the study, but he has read the abstract, and the abstract is ambiguous in the decisive sentence. He is not stupid. He is thorough. That is the problem.

The backwards diagnostician. She has the diagnosis first and looks for the symptoms afterwards. She has read that histamine intolerance manifests through fatigue, headaches, bloating, palpitations, skin flushing, sleep disturbances and mood swings, and finds that all of it applies to her. She is right. It applies to all of us. That is precisely the charm of diagnoses that explain everything.

The symptom-checker athlete. He has three apps and enters slightly different information into each until one of them produces something reassuring. If none does, he enters the symptom again and leaves out the fever. This procedure has a name — data manipulation — and it is punished considerably more severely in research than at the kitchen table.

The relative by proxy. She is not ill. Her husband is ill, he just does not know it yet. She describes his symptoms with a precision he would never manage himself, and she is entirely right that he should finally see a doctor. She is, incidentally, the most valuable customer of the day, because her suspected diagnoses are astonishingly often correct.

The self-optimiser. He comes not with an illness but with a laboratory value he has had measured privately, and an order list of nine preparations. He has no symptom. He has a goal.

And the premier class: the TikTok diagnosis. A thirty-nine-second video, backed by sad piano music, text: “5 signs your cortisol is destroying you”. Sign one: you are tired. Sign two: you have belly fat. Sign three: you are sometimes irritable. There follows a link to a powder.

The finest misdiagnoses from everyday practice

The classics are well known and magnificent every time.

The muscle soreness after the first day’s skiing that becomes Lyme disease, because ticks come in spring and skiing is somehow nature. The tingling in the hand that appears after four weeks of using the phone lying down and means a stroke. The coated tongue that indicates a systemic fungal disease which, according to the internet, is responsible for practically every human complaint and can be treated exclusively by a diet in which nothing that brings joy may be eaten.

Particularly fine is the category of geographically improbable diagnoses. The gentleman from the Mittelland who is certain he has malaria. He has never been in a malaria area. He has been to Rimini. But he had a fever, and fever is on the list.

And then there is the genre of self-diagnosis by excluding all normal explanations. The headache cannot possibly come from yesterday’s wine, because it was only two glasses, well, three, essentially a bottle, but good wine does not cause headaches.

Why this happens, and not out of stupidity

The reason lies less with people than with the tools.

In the best-known investigation on the subject, 23 symptom checkers were tested with 45 standardised case vignettes. The correct diagnosis came first in 34 per cent of cases, in the top three in 51 per cent, and among the first twenty possibilities named at all in 58 per cent. The triage recommendation was likewise correct in 58 per cent, with the systems performing better on the critical cases than on the harmless ones.

Translated: two out of three times the first suggestion is wrong, and in four out of ten cases the correct answer does not appear in a list of twenty at all. Anyone who also bears in mind that every one of these systems, for liability reasons, would rather point to catastrophe once too often than once too rarely will understand how a twitching eyelid becomes a neurodegenerative disease.

Added to this is the economics of the internet. No algorithm is rewarded for someone falling asleep reassured. What is rewarded is clicking on. “This is harmless, go to bed” is the worst content in the world.

And now the uncomfortable part

Before we get too comfortable: Dr Google is sometimes right, and embarrassingly often in precisely those cases where the professional world was wrong for a long time.

The woman who accepted severe period pain as normal for years and reads the word endometriosis for the first time on the internet. The adult who at forty finds an explanation for a life full of missed deadlines. The person with unclear complaints who recognises themselves in a forum because someone there describes exactly the same strange combination.

These people are not hysterical. They are affected by a system that told them for years it was nothing. The internet gave them a word, and a word is the beginning of every investigation.

The art therefore does not lie in laughing self-diagnoses away. It lies in distinguishing between the malaria from Rimini and the endometriosis after eight years. Search engines cannot do that. People with professional training can.

The art of bringing someone down without humiliating them

The worst sentence is: “You certainly don’t have that.” It is usually true and never helps, because it devalues the research and thereby the person.

The best sentence goes roughly like this: “Your research was not wrong. It was just incomplete, because the internet does not know your history. Tell me about it from the beginning.”

Then you listen, sort, name the most likely explanation, say honestly what you cannot rule out, and state the condition under which it should be investigated. Done. That takes four minutes, costs nothing and is the only intervention in this text with demonstrated efficacy.

And when someone stands before you with fourteen double-sided pages, remember: this person invested half an evening in trying to understand what is going on with their body. They just used the wrong tool.

The right one stands behind the counter and does not laugh.