Eczema rates have jumped up to sixfold since 1970, and industry may explain why
Since 1970, atopic dermatitis has become three to six times more common in the United States and Britain. Children who move from developing countries to industrialised ones before age four see their risk climb sharply. One line of research points to two industrial chemicals whose production surged from that same year.
Atopic dermatitis, often just called eczema, is a long-lasting inflammation that leaves skin itchy, red, swollen and cracked; long-standing patches thicken, a change called lichenification. About one person in five has it at some stage. It usually begins in childhood and is slightly more common in girls and women. The affected areas move with age: babies get it on the face and limbs, older children in the creases of the knees, elbows and neck, and adults often on the hands and feet. Many patients also develop hay fever or asthma.
No single cause is known. Genes matter a great deal: if one identical twin has it, the other has an 85 percent chance. About 30 percent of patients carry mutations in the filaggrin gene, which helps build the skin barrier, and up to 80 percent have raised levels of the allergy antibody IgE. When the barrier fails, allergens get deeper into the skin and set off a type 2 immune response driven by signalling molecules such as IL-4 and IL-13. Scratching damages skin further, and the bacterium S. aureus exploits the breaks, feeding a chronic loop. The condition itself is not contagious, and stress can worsen it without causing it.
The industrial idea centres on diisocyanates and xylene. These chemicals stop skin bacteria from making certain protective lipids, and children short of those lipids early in life are more likely to develop the disease. They also switch on TRPA1, an itch receptor in the skin. They turn up in car exhaust, wildfire smoke, paints, cigarette smoke, foam furniture and fabrics such as polyester and spandex.
Other clues fit the hygiene hypothesis, which holds that early contact with microbes trains the immune system. Growing up with dogs, drinking unpasteurised milk and helminth infections all appear protective. Hard household water may raise the risk in early life, though softening water does not ease established eczema. Cold, dry air and dust mites tend to trigger flares. Treatment rests on moisturisers, steroid creams to calm flares and, for severe cases, systemic drugs such as dupilumab.
Source: Atopic dermatitis
