Broxbourne House, based on Barnsley Road, was rated inadequate by the Care Quality Commission (CQC) after a visit by the regulator in October.
Inspectors found a number of failings at the home, which cared for 21 elderly residents at that time.
The home's management said they were already making improvements to the service's following the CQC's findings.
In their report, inspectors said that residents' "were not treated with respect and their privacy and dignity was not maintained".
They said: "Bedding and towels were worn, discoloured and some were torn; towels, face cloths, duvet covers, pillowcases and sheets were all piled in a cupboard in a bathroom.
"Most people did not have their own toiletries; a member of the management team showed us a cupboard in the laundry which had communal body wash, shampoo and body spray. They said these items were used for people."
Although the health watchdog did praise some individual social workers at the home, they also reported examples of poor practice.
They added: "One member of staff assisted a person to eat their breakfast. They did not speak to the person and just spooned the food into their mouth and wiped food from the person's mouth using the bottom of the clothes protector.
"They then attempted to give the person a drink while the person's mouth was still full of food. Some people were given spoonfuls of food by different staff as they were walking past."
Residents and their families also reported there was little for them to do at the Broxbourne House, with one relative saying, "My husband is down in the dumps; his social skills are deteriorating. There is a lack of interaction, he's very bored."
The home was given an inadequate rating for four out of the five categories used by the CQC to assess care facilities.
The report said: "The overall rating for this service is 'Inadequate' and the service is therefore in 'special measures'."
A spokesman for the home said he was confident that it would improve swiftly.
He said: "We've got six months now. We've got an action plan in place and we're working hard on that.
"We've got people in from outside agencies who can help us."
Local Democracy Reporting Service