The French Institute of Health and Medical Research, or Inserm, describes atopic dermatitis or atopic eczema as “a chronic inflammatory skin disease characterised by dry skin associated with eczema-like lesions (redness and itching, vesicles, oozing and crusting)”.

The research organisation points the finger at genetic and environmental factors. Indeed, numerous scientific studies around the world have reported an increase in the number of cases of this chronic disease – particularly in industrialised countries – in connection with environmental changes and lifestyles.

This finding has led researchers from the University of California, San Francisco (UCFS) to investigate the impact of an everyday ingredient on skin dryness, itching and, more broadly, on eczema.

To do this, they analysed data from 215,832 adults aged 37-73 from the UK Biobank – a large-scale, long-term study assessing the influence of genetic predisposition and environmental exposure on the development of numerous diseases.

Urine samples and electronic medical records were analysed to determine the amount of sodium, a component of salt, consumed by the participants, and to correlate this data with a possible diagnosis of atopic dermatitis.

Published in the journal Jama Dermatology, their research shows an increased risk of eczema diagnosis (+11%), eczema cases (+16%), and chronic disease severity (+11%) for each additional 1g of sodium excreted in the urine over a 24-hour period.

To support these findings, the researchers examined data from another population: 13,014 American adults from the National Health and Nutrition Examination Survey. And the findings were similar: consuming an extra 1g of sodium per day – the equivalent of half a teaspoon of table salt – was associated with 22% higher odds that someone would have an active case of eczema.

The experts, therefore, advise patients to limit their salt intake to better manage eczema flare-ups.

“Most Americans eat too much salt and should safely reduce their intake to recommended levels,” said Katrina Abuabara, associate professor of dermatology at UCSF. “Eczema flare-ups can be difficult for patients to cope with, especially when they are unable to anticipate them and don’t have recommendations on what they can do to avoid them.”

According to data shared by the National Eczema Association, around 2.4% of the global population has some form of eczema. This includes 31.5 million people in the US alone, or around 10% of its population.