The mother of a teenage girl believed to be missing says her daughter has a severe allergy, which is life threatening.

Police are appealing for information about Brookelyn Brand, 14, who has been missing for six nights and could could be in Levin or Napier.

Central District police put out a call on Facebook for sightings of the teenager, saying they had concerns for her safety.

Her mother, Mishele Pou, told ONE News Brookelyn was allergic to all kinds of nuts and she was worried she may not have an EpiPen with her.

"My main concern is that she has a severe allergy because she's anaphylactic... it's life threatening," the Auckland mother said.

Pou told ONE News Brookelyn wasn't coping with school in Auckland and wanted to return to the Horowhenua area where her father lives.

"We've lost her twice before and we've tried contacting her on her phone and through social media but she has blocked us," she said.

"She's blocked all her family from contacting her on social media."

Her mother believed she might be mixing with the wrong crowd in the Levin and Napier area, where she is believed to be.

"Please Brookelyn call or txt me to let me know you're safe," she told ONE News.

"I've never stopped loving you and the door here is always open."

Stuff understands Brookelyn had gone missing before, in November 2015, and was found about a week later.

A police spokeswoman said the last time Brookelyn was seen was when she left her home last Thursday afternoon.

Any information about her whereabouts can be supplied to police by messaging the Central District police Facebook page, calling the nearest police station, or anonymously through the Crimestoppers line, on 0800 555 111.