Hairdressers have noticed a rise in the number of people having allergic reactions to hair dye after recovering from Covid.
Anecdotal evidence indicates that people who have caught the virus, recovered and later gone to have their hair coloured have suffered severe reactions to various products.
A woman named Gemma, who had Covid in January, told the BBC: "The reaction is so severe. My whole scalp, my face – I just can't even imagine what would have happened to me."
She was asked to come into the salon at least two days before her appointment to do a patch test for allergy to the dye under new guidance from the National Hair and Beauty Federation (NHBF). The test sees a blob of dye put on the customer's skin to check that it is safe for use on them.
The step was implemented as a result of reports of more allergic reactions than normal in customers. Gemma said she thought it was "a bit of a faff" because she had used the same product for a decade – but suffered a potent reaction when she had the test.
"The following day, I felt a really hot burning sensation behind my ear which progressively got worse to the point where it had taken layers of my skin from behind my ear," she said. The salon said it had seen four other similar instances.
The coronavirus that causes Covid is known to have a severe impact on the immune system, and experts at Imperial College London are looking at whether there are any long-term changes to a person's immune system following infection and, if so, how long they last.
Dr David Basketter, consultant toxicologist at DABMEB Consultancy Ltd, told The Telegraph: "Permanent hair dyes are a real allergy risk and awareness of this is rising, such that upon return to salons there is a greater chance that they will insist on an allergy test prior to dyeing.
"Thus, without the need to invoke Covid's impact on the immune system, one might expect to see a greater number of hair dye reactions, which does not mean that there isn't a Covid effect as well."
Richard Lambert, the NHBF chief executive, said: "There is no scientific evidence to support the claim that having Covid alone increases an allergic reaction to hair colour or any other hair and beauty treatments. An allergic reaction can occur at any time due to a number of factors, of which a compromised immune system is one."