The latest blow to the San Francisco-based home rental site comes from a Rutgers University study that found that prospective renters who identified themselves as having disabilities were more likely to be rejected for lodging than those who did not mention having a disability.
"It raises some troubling questions about who we are sharing with," said Mason Ameri, a Rutgers University professor who worked on the study. "Are we only sharing with people who resemble ourselves?"
Airbnb disputed parts of the study and repeated its commitment to treating all users fairly.
"Discrimination of any kind on the Airbnb platform, including on the basis of ability, is abhorrent," the company said in a statement. The company also noted that it has created an anti-discrimination task force to root out bias among people who list properties for rent on the site.
The 1990 Americans with Disabilities Act requires hotels and other public places to make accommodations for people with disabilities but it does not apply to lodging with five or fewer rooms as well as places occupied by the resident of the home.
Still, Airbnb — responding to accusations of racial discrimination by hosts — required all users last year to agree to abide by a policy that forbids discrimination based on race, religion, national origin or disability.
Researchers at Rutgers made 3,847 lodging requests on the Airbnb platform, using profiles for fictitious travelers including some who identified themselves as being blind or having cerebral palsy, dwarfism or spinal cord injuries.
The study found that hosts approved 75% of guests who didn't mention having a disability but only 61% of those who said they had dwarfism, 50% of guests who said they were blind, 43% for those with cerebral palsy and 25% with a spinal cord injury.
The Rutgers study sent out the lodging requests between June 1 and Nov. 15, 2016.
The study found little difference in how Airbnb hosts responded to requests from guests with disability before and after Airbnb adopted the nondiscrimination policy on Sept. 8, 2016.
Those disparities also did not change much among Airbnb hosts who advertised that their lodging was wheelchair accessible.
"The overall results indicate that this new institutional form creates substantial challenges in ensuring equal access for people with disabilities," the study concluded.
Airbnb, the nation's biggest short-term rental site, came under fire last year after a Harvard Business School study revealed that guests with traditionally black names are more likely to be denied a booking than others.
The Rutgers study was prompted by a professor who wanted to know if the growing sharing economy is sharing equally with people with disabilities, Ameri said.
Some hosts who rejected the requests for lodging explained that their homes were not accessible to people with disabilities.
One host rejected a request from a fictitious guest with cerebral palsy, saying "our place has a very narrow and circular stairway so it would be too difficult for you," according to the study. Some hosts tried to charge extra for guests with service dogs, despite an Airbnb policy prohibiting such a fee, the study found.
But several of the hosts who approved reservations for the fictitious guests with disabilities were accommodating.
Responding to a traveler who was described as having a spinal cord injury, one host said: "We do have two steps up to the front porch but we'd be happy to assist you."