A Sydney mother claims she suffered second-degree burns after falling asleep with her iPhone 7 charging while resting on her arm.

Melanie Tan Pelaez said she fell asleep while watching movies on her phone and woke up with pins and needles down her arm on October 31.

"I went to get dressed and realised my arm was very red, so I then went to the GP and they advised me I needed to go straight to the hospital," the pregnant mother told news.com.au .

Ms Tan Pelaez was told to check around her bed for what could have burnt her and quickly identified her phone as the culprit, matching the device and charger with the marks on her arm.

She said she took to the phone to an Apple store where staff initially said the device could not have burnt her because it did not have "a distinct smell".

"I then got a call from a member of the executive team who told me they were now handing the matter and had sent the phone to a senior technician in California for testing," Ms Tan Pelaez said.

She said she was offered a replacement phone but rejected the offer because she no longer trusted the device.

Ms Tan Pelaez has also warned others about the phone on Facebook.

She has since been to the emergency room twice and may need to undergo plastic surgery to heal the scars left on her arm.