Some Welsh nurses are complaining of skin irritation from their new uniform. Authorities are investigating.
Those affected have been told to wear their old uniforms while tests on the fabric and dye are carried out.
Nurses in Hywel Dda and Betsi Cadwaladr University health boards were the first in Wales to wear the new tunic-style colour-coded uniforms two weeks ago.
But within hours of putting the new uniforms on, some nurses started to develop an itch and a rash.
One nurse affected by the problem said: "Me and 10 of my colleagues, and more I know of around the hospital, have developed the most unbearable rash since wearing these new uniforms.
"Advice we have received from dermatology is to stop wearing them to give our skin a chance to recover and to wear our old uniforms which we still have.
"I will be wearing my old uniform and my constant scratching will hopefully ease so that I stop frightening my patients."
The new national nurse uniforms - the first of their kind in the UK - are made from a blend of polyester (67%) and cotton (33%) by the company Alexandra Plc.
The uniforms are dyed a different shade of blue or green depending on a nurse's grade - ward sisters wear navy blue; staff nurses wear hospital blue; midwives wear postman blue and healthcare support workers are turned out in green.
The uniforms underwent extensive testing before they were introduced.
A range of new tests are now being carried out on the fabrics and the dye.
The results are expected later this week, Western Mail reported.
Rosemary Kennedy, Wales' chief nursing officer, said: "Although only a minority of nurses have reported skin irritation, we are concerned as the welfare of our staff is paramount.
"We will continue to monitor the situation and the two health boards are ensuring that those experiencing discomfort have full support from their occupational health team.
"As only a minority of staff have reported a problem, we have sufficient supplies of alternative uniforms for use. We are also working in partnership with the Royal College of Nursing (RCN) and Unison to address any concerns as quickly as possible.
"We are disappointed with this news, as the fabric used to manufacture the uniforms underwent extensive testing and quality control by both the suppliers and an independent accredited testing body before the contract was awarded.
"Extensive wearer trials were also undertaken and no skin irritation was reported.
"Robust testing of the fabric is currently being undertaken by an independent body to establish the exact nature of the problem and, through our contractual arrangements, we expect the manufacturers to put this right."
Tina Donnelly, director of the Royal College of Nursing in Wales, said: "When any new uniform is introduced there are always some skin irritations."