Julia McCabe, 38, stopped breathing after what her family believe was a reaction to a chemical in the dye.
The mother-of-two, who is from Keighley in Yorkshire, is in a coma on life support in Airedale General Hospital with her family by her side.
The Yorkshire Post says her father, Keith Miller, has been warned that his daughter may not survive.
Mrs McCabe had used the dark-coloured L'Oreal Preferences dye but then started to feel ill and told her husband Russell she was struggling to breathe.
Mr Miller, of Shipley, added: "She finished dyeing her hair and said 'I don't feel well, I can't breathe', to her husband. He rushed her to hospital.
"She is in a coma. We've spoken to the doctors and they have more or less said to us the condition she is in now is most likely how she will stay. They are not giving us much hope. It's hard to take in."
Mr Miller said he believes a chemical called para-phenylenediamine (PPD) caused his daughter's condition.
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