The Itch That Rashes
Scientists have pinpointed a reason why eczema sufferers often experience an itch before a rash appears: Staphylococcus biofilm. Itching and inflammation not yet visible on the skin’s surface are the result of bacteria-blocked sweat ducts.
The research team, headed by Herbert B. Allen, MD, professor and chairman of the department of dermatology at Drexel University College of Medicine in Philadelphia, PA, sought to determine the role Staph—known to be present in eczema or atopic dermatitis—played in causing the itch. In a study1 of 40 patients with atopic dermatitis, researchers collected routine swabs from lesional and nonlesional skin—all contained multidrug-resistant staphylococci. All the tests were positive for biofilm.
According to Allen, eczema is worse in the presence of sweating. When the staphylococci are exposed to the salt water in sweat, they produce a biofilm that clogs the ducts. This, in turn, evokes an immune response, which causes the itch and rash.
The hallmark of eczema is red, scaly patches on the skin—particular on the head and scalp, neck, inside of elbows, behind knees, and buttocks. Genetics may play a role as persons with eczema frequently exhibit a gene mutation, filaggrin, which also predisposes them to asthma. The mutation does contribute to a compromised outer layer of skin, but the exact cause of eczema is still unknown.
Note: Eczema is 3 times more prevalent among persons with celiac disease and about 2 times more frequently seen in relatives of persons with celiac disease, thus underscoring the potential for a genetic tie-in.2
Toll-like receptor 2 is the protein that is involved in the innate immune system, which is activated in areas where there are blocked sweat ducts in cases of eczema. Biofilm, communities of microbial cells surrounded with secreted polymers, appear to be the obtrusive culprit; they work by stimulating the body’s defenses against the tenacious S aureus bacteria. The National Institutes of Health reports that more than 65% of all microbial infections are caused by biofilm.3 In fact, biofilm is often implicated in chronic, nonhealing wounds.
Current management for eczema includes the use of steroids to reduce inflammation and enhance the body’s ability to fight the bacteria. Patients should be instructed to be wary of soap, hot water, scrubbing, and clothing that can aggravate itching, scratching, and peeling. Oil rather than water-based moisturizers are recommended. Products containing dyes, perfumes, or peanuts should be avoided.
Nighttime use of occlusive dressings may be helpful. Corticosteroids should be reserved for use during flares. Short-term, fixed periods of use of topical immunosuppressants (eg, pimecrolimus and tacrolimus—the latter may work better than the former) are additional options for patients who do not respond to and/or cannot tolerate steroids.
Attention to diet, other than the aforementioned allergens, appears to have no effect. Some clinicians may recommend washing with a mild solution containing bleach, but such practices must be carefully guided to avoid compromising the outer layer of skin. Finally, persons with eczema should not be vaccinated for smallpox because of the risk for eczema vaccinatum, a potentially severe and sometimes fatal complication.
Note: Current research indicates that eczema patients with diseases, such as seborrheic dermatitis, granular parakeratosis, prickly heat, and tinea pedis (athlete’s foot), should be examined to determine whether occluded ducts are a consideration.
“Even though bacteria and their biofilms are present, ordinary treatments with topical corticoids are successful in at least 95% of patients if good skin care is practiced—less soap, less hot water, less bathing, less scrubbing along with more moisturizing,” Allen said to Consultant360.
The study did not mention any additional treatment for the Staph infection.
Given today’s climate of drug-resistant bacteria, the best approach is to augment the body’s ability to address the inflammation and subsequent itch, particularly when treating patients with chronic conditions like eczema. Before you dismiss a patient with an itch and an unseen rash, keep in mind lurking biofilms may be to blame. ■
1. Allen HB, Vaze ND, Choi C, et al. The presence and impact of biofilm-producing staphylococci in atopic dermatitis. JAMA Dermatol. 2014 Jan 22. [Epub ahead of print]
2.Ciacci C, Cavallaro R, Iovino P, et al. Allergy prevalence in adult celiac disease. J Allergy Clin Immunol. 2004;113:1199-1203.
3.Costerton JW, Stewart PS, Greenberg EP. Bacterial biofilms: a common cause of persistent infections. Science. 1999;284: