Physicians are aware that climatic conditions negatively affect the skin. In particular, people living in equator far countries such as the Northern parts of Europe and North America are exposed to harsh weather during the winter and may experience dry and itchy skin, or deterioration of already existing dermatoses. We searched the literature for studies that evaluated the mechanisms behind this phenomenon. Commonly used meteorological terms such as absolute humidity, relative humidity and dew point are explained. Furthermore, we review the negative effect of low humidity, low temperatures and different seasons on the skin barrier and on the risk of dermatitis. We conclude that low humidity and low temperatures lead to a general decrease in skin barrier function and increased susceptible towards mechanical stress. Since pro-inflammatory cytokines and cortisol are released by keratinocytes, and the number of dermal mast cells increases, the skin also becomes more reactive towards skin irritants and allergens. Collectively, published data show that cold and dry weather increase the prevalence and risk of flares in patients with atopic dermatitis.

We observed that early exposure to hard domestic water and a fall/winter birth was associated with an increase in the relative prevalence of AD within the first 18 months of life. Although the 2 exposures did not interact synergistically, a dose-response relationship was observed between domestic water hardness and AD.

Patients with atopic dermatitis (AD) have skin barrier impairment in both lesional and nonlesional skin. They are typically exposed daily to emollients and intermittently to topical anti-inflammatory medicaments, thereby increasing the risk of developing contact allergy and systemic exposure to chemical ingredients found in these topical preparations. We systematically searched for studies that investigated skin absorption of various penetrants, including medicaments, in patients with AD, but also in animals with experimentally-induced dermatitis. We identified 40 articles: 11 human studies examining model penetrants, 26 human studies examining AD drugs, and three animal studies. We conclude that patients with AD have almost twofold increased skin absorption compared with healthy controls. There is a need for well-designed epidemiological and dermatopharmacokinetic studies that examine to what extent AD causes patients to be systemically exposed to chemicals compared with nonatopic dermatitis.