Eczema (Atopic Dermatitis)

Atopic dermatitis, also called eczema, is a common skin condition. "Atopic" refers to a heightened sensitivity toward allergens, leading to frequent, excessive immune reactions that inflame and irritate the skin (dermatitis). Other atopic diseases include allergic rhinitis and asthma. It is most common during childhood, with a prevalence of up to 25% of children affected, but can persist into adulthood; over a lifetime, 7–10% of people will get eczema at some point.^[1]

Red, inflamed skin lesions that can occur on many parts of the body. These lesions are dry and often itchy, swollen, oozing, crusting, and with time can become lichenified (thick and leathery). Scratching is common, which leads to a vicious cycle of irritation leading to scratching leading to further irritation. Psychological symptoms such as depression, anxiety, and insomnia are also common.

Diagnosis is generally based on signs/symptoms and medical history. Eczema is chronic, so it can take a while to be sure that the lesions are due to eczema rather than a more acute phenomenon like an infection, an acute or transient allergic reaction, or exposure to harmful chemicals. A history or family history of asthma, hay fever, and dry skin also makes eczema more likely. To determine the severity of atopic dermatitis and track treatment progress, researchers and doctors objectively measure several characteristics of the lesions with scoring systems such as EASI and SCORAD.^[2]

The use of topical barrier creams and topical corticosteroids, such as hydrocortisone, are typically the first line of treatment. Oral and topical antihistamines are also commonly used early. If this proves insufficient, immunosuppressive (focused on curtailing the excessive immune system activation) drugs are frequently employed. Some such drugs and drug types include monoclonal antibodies, JAK inhibitors, steroids, calcineurin inhibitors, methotrexate, mycophenolate mofetil, and cromoglycate. Phosphodiesterase inhibitors are also sometimes used to induce vasodilation.

Several supplements have and continue to be investigated for eczema, though at present, the only ones approaching credibility from clinical trials are vitamin D^[3] and probiotics.^[4] They are also mechanistically plausible. Vitamin D is known to help regulate the immune system and plays a role in the formation of filaggrin, which helps to maintain the skin's moisture barrier. Some probiotics play a significant role in regulating the immune system to reduce excessive inflammation, maintain the gut barrier and prevent further inflammation.

The use of partially hydrolyzed whey protein infant formula may reduce the risk of eczema later in life.^[5] In addition, sufficient levels of vitamin-d, zinc, and selenium are associated with a lower risk of eczema, though besides vitamin D, it's not clear if they are causally linked.^[6]

Fabric selection may play a meaningful part in reducing itching. Fabrics with scratchier fibers and wider spaces between fibers, such as wool, are worse, whereas cotton, silk, and ultrafine wool may be better choices.^[7] There is also interest in a number of alternative fabrics treated with antibacterial agents, such as silver, zinc oxide, and borage oil, with some clinical evidence in particular for silver, though more research is needed.^[8] Phototherapy with narrow-band UV-B and UV-A1 has also seen a considerable amount of research and is likely effective for reducing the severity of eczema.^[9]

Genetics plays a considerable role, and a number of mechanistically plausible genes have been linked to eczema risk.^[10] Additionally, microbiome disruption is highly common in eczema, and with the vital role in immune regulation that the microbiome plays, this is plausible.^[11] Other possible factors include smoking, maternal alcohol consumption and stress/anxiety, being born in winter, phthalate exposure, and hard water. The early-life use of antibiotics^[12] and acetaminophen are also associated with eczema, though it's possible that this is due to a dysfunctional immune system leading both to the need for those medications as well as eczema.