The cause of<unk>  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<unk> . Genetics Many people with<unk>  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,<unk> , or hay fever. Up to 80% of people with<unk>  have elevated total or allergen-specific IgE levels. About 30% of people with<unk>  have mutations in the gene for the production of filaggrin (FLG), which increase the risk for early onset of<unk>  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<unk> . Those exposed to dogs while growing up have a lower risk of<unk> . Also, epidemiological studies support a protective role for helminths against<unk> . Likewise, children with poor hygiene are at a lower risk for developing<unk> , as are children who drink unpasteurized milk. Allergens In a small percentage of cases,<unk>  is caused by sensitization to foods. Also, exposure to allergens, either from food or the environment, can exacerbate existing<unk> . Exposure to dust mites, for example, is believed to contribute to one's risk of developing<unk> . A diet high in fruits seems to have a protective effect against<unk> , whereas the opposite seems true for fast foods.<unk>  sometimes appears associated with celiac disease and nonceliac gluten sensitivity, and the improvement with a gluten-free diet (GFD) indicates that gluten is a causative agent in these cases. Role of Staphylococcus aureus Colonization of the skin by the bacterium S. aureus is extremely prevalent in those with<unk> . Abnormalities in the skin barrier of persons with<unk>  are exploited by S. aureus to trigger cytokine expression, thus aggravating the condition. Hard water<unk>  in children may be linked to the level of calcium carbonate or "hardness" of household water, when used to drink. So far, these findings have been supported in children from the United Kingdom, Spain, and Japan.
Atopic dermatitis
Scabies
Orofacial granulomatosis
Seborrhoeic dermatitis
Noxzema
Rodent mite dermatitis
Essential dermatitis
Phototoxic tar dermatitis