Two and a half years into his term, President Donald Trump is solidifying his standing as the most germ-conscious man to ever lead the free world. His aversion shows up in meetings at the White House, on the campaign trail and at 30,000 feet. And everyone close to Trump knows the president’s true red line.

“If you’re the perpetrator of a cough or of a sneeze or any kind of thing that makes you look sick, you get that look,” said a former Trump campaign official. “You get the scowl. You get the response of — he’ll put a hand up in a gesture of, you should be backing away from him, you should be more considerate and you should extricate yourself from the situation.”

The president’s admitted germaphobia has been a fixture throughout his career — from real-estate deal rooms to casino floors — and it’s now popping up in more public ways. It could create another round of tactile challenges as Trump launches his 2020 campaign, during which he might try to steer visitors toward his signature thumbs-up selfies and away from handshakes for the next 16 months.