Why? He can no more answer that than Johnson can tell you why she needs to chew her food in sets of three bites or drink her beverages three sips at a time. Three is her magic number. That is about as refined an explanation as any of us can give for our compulsions, rituals that we understand are entirely illogical.

And waiters, waitresses and bartenders. For some with obsessive-compulsive disorder, the success or failure of a dining experience can hinge on the appearance of a restaurant’s staff.

Solomon, for example, feels compelled to inspect the hands of anyone serving him. Cuts and scrapes are objectionable because in his mind, they can lead to his contracting a disease that could kill him.

Recently, Solomon ate at the bar where he noticed a small red stain on the bartender’s right knuckle, and thought it was blood. Trying to avoid things the bartender had touched, he used a straw to drink water and swapped the silverware.

Jared Kant, a 24-year-old research assistant in Boston who has obsessive fears of contamination, once insisted on sterilising all utensils at a Chinese restaurant table by holding them above a small flame at the center of a pu-pu platter.

Coincidentally, Solomon and Kant have each battled contamination issues on both sides of the counter. Solomon spent years working as a bartender, often consumed by thoughts of becoming deathly ill. He was convinced that one of his regular customers was carrying a fatal virus, and came up with strategies to minimize contact. “I would always quickly put his change down before he could try to take it from my hand,” he said.

... contd.