Anna Maria, one of the favourites to win this season, was left scratching her head wondering where she had picked up the itchy pests.
"No idea where they came from. I tried on a hat while shopping," the pouty 16-year-old brunette said on Thursday night's episode.
The show's producers speculated she also might have gotten the bugs at New York Fashion Week.
Not known for their good timing, the head lice appeared just as the modelling hopefuls were supposed to strut their stuff for a special "sexy edition" of Klum's show.
The German supermodel, who recently announced she would celebrate her upcoming 40th birthday in June with a hat party, did not say if the lice plague had caused her to reconsider her plans.