A study assessing people’s risk of primary biliary cirrhosis has found that hair dye and smoking both increase the risk of progressive liver disease.
The study was based on more than 4,600 people, assessing their risk of primary biliary cirrhosis.
The researchers in Manchester and Newcastle found smoking increased the risk by 63% while hair dye increased it by 37%.
Previous bouts of urinary infection, psoriasis and shingles also increased the risk, as did autoimmune diseases such as rheumatoid arthritis, thyroid and coeliac diseases.
People in the study were not asked how often they dyed their hair and it is unclear which part of the hair dye may be responsible for the effect, the experts said.
However, previous studies have noted a link between cirrhosis and a chemical found in cosmetics called octynoic acid, which is used in hair dye and nail polish.