WADI KHALED, Lebanon — The modest shelter housing some Syrian refugees here, a few hundred yards south of the border with Syria, hardly looks objectionable. Made of plywood walls on a concrete foundation of some 250 square feet, with one door, two windows and a corrugated zinc roof, the squat structure is called a “box shelter.”

But Lebanon has banned box shelters, regarding them as a threat to this already fragile nation. In the eyes of the Lebanese, the box shelters, made by the Danish Refugee Council, look too permanent and could encourage the Syrians to stay.

“The fear of permanence is very embedded in the Lebanese political psyche,” said Makram Malaeb, a manager in the Syrian refugee crisis unit at the Ministry of Social Affairs. “We had Palestinian refugees who were supposed to stay here for a month in 1948, and now they are a population of 500,000. And we went through a 15-year civil war where the Palestinians were a large player.”

Of the many factors complicating the world’s response to the Syrian refugee crisis, none are perhaps more peculiar to the Middle East than Lebanon’s deep-seated fear of permanence. The Lebanese have so far rejected the establishment of any refugee camp, citing their long, troubled history with Palestinian camps on their soil. Acutely aware of the history of refugee housing — flimsy tents that metamorphosed over decades into concrete multistory dwellings — the Lebanese view even the most modest of new shelters for Syrians with suspicion.