Lichenification, excoriation, and erosion or crusting on the trunk may indicate secondary infection. Flexural distribution with ill-defined edges with or without hyperlinearity on the wrist, finger knuckles, ankle, feet, and hands are also commonly seen. Causes
The cause of AD is not known, although  some evidence indicates genetic, environmental, and immunologic factors. Climate
Low humidity, and low temperature increase the prevalence and risk of flares in patients with atopic dermatitis. Genetics
Many people with AD have a family history or a personal history of atopy. Atopy is an immediate-onset allergic reaction (type-1 hypersensitivity reaction mediated by IgE) that may manifest as asthma, food allergies, AD, or hay fever. Up to 80% of people with atopic dermatitis have elevated total or allergen-specific IgE levels.About 30% of people with atopic dermatitis have mutations in the gene for the production of filaggrin (FLG), which increase the risk for early onset of atopic dermatitis and developing asthma. Hygiene hypothesis
According to the hygiene hypothesis, early childhood exposure to certain microorganisms (such as gut flora and helminth parasites) protects against allergic diseases by contributing to the development of the immune system. This exposure is limited in a modern "sanitary" environment, and the incorrectly developed immune system is prone to develop allergies to harmless substances. Some support exists for this hypothesis with respect to AD. Those exposed to dogs while growing up have a lower risk of atopic dermatitis. Also, epidemiological studies support a protective role for helminths against AD.
The mild to moderate proximal interphalangeal (PIP) joint flexion and extension contractures and stiff distal interphalangeal (DIP) joints in slight flexion often seen in sclerodactyly can be addressed somewhat with physical therapy. In a few cases when immune involvement isnt apparent (in these cases environmental causes are suspected), the condition may gradually clear up by itself If the trigger is avoided. In other cases, early treatment while the disease is in the inflammatory stage is much more likely to be successful than on established lesions. See also
Hand eczema
Atopic dermatitis


== References ==