Eczema causes red, itchy, inflamed patches on the skin
Adding bleach to the bath may be an effective treatment for chronic eczema, US researchers say.
In a study of 31 children, there was significant improvement in eczema in those who had diluted bleach baths compared with normal baths.
The Pediatrics study also showed improvements were only on parts of the body submerged in the bath.
UK experts stressed the treatment could be extremely dangerous and should only be done under the care of a specialist.
Children with bad eczema suffer from chronic skin infections, most commonly caused by Staphylococcus aureus, which worsen the eczema that can be difficult to treat.
Some children get resistant MRSA infections.
Studies have shown a direct correlation between the number of bacteria on the skin and the severity of the eczema.
It has been shown that bacteria cause inflammation and further weaken the skin barrier.
In the study, researchers randomly assigned patients who had infection with Staphylococcus aureus to baths with half a cup of sodium hypochlorite per full tub or normal water baths for five to 10 minutes twice a week for three months.
They also prescribed a topical antibiotic ointment or dummy ointment for them to put into their nose - a key site for growth of the bacteria.
Eczema severity in patients reduced five times as much as those on placebo.
But there was no improvement in eczema on the head and neck - areas not submerged in the bath.
"We've long struggled with staphylococcal infections in patients with eczema," said study leader Dr Amy Paller, from Northwestern University in Chicago.
She added they saw such rapid improvement in the children having bleach baths that they stopped the study early.
"The eczema kept getting better and better with the bleach baths and these baths prevented it from flaring again, which is an ongoing problem for these kids.
"We presume the bleach has antibacterial properties and decreased the number of bacteria on the skin, which is one of the drivers of flares."
Professor Mike Cork, head of dermatology research and a consultant at Sheffield Children's Hospital, said antiseptic baths had been used as a treatment for eczema for quite a while but the trial was important because it highlights the benefits from reducing bacteria.
"But people should not start putting bleach in their children's bath.
"Bleach used incorrectly could cause enormous harm to a child with atopic eczema while, in the hands of an expert, it can as this trial indicates lead to benefit."
He added the trial highlighted the need for children with uncontrolled eczema to be referred to a specialist for treatment.