Phthalate esters in plastics act as adjuvants for
immunoglobulin production, which aggravates allergic disease. However, the effects of alkylphenols (used as
plasticizers and
surfactants) on
atopic dermatitis have not been studied in detail. Therefore, the goal of the present study was to investigate the effects of the alkylphenols
4-nonylphenol (NP),
4-tert-octylphenol (OP) and
4-tert-butylphenol (BP) in a murine model of
atopic dermatitis. NC/Nga mice were intraperitoneally administered NP, OP or BP and were subcutaneously injected with mite
allergen in one ear to induce
atopic dermatitis-like skin lesions (ADSLs). The condition of the skin was observed, and the levels of
immunoglobulin in serum and inflammatory
cytokines in lesions were determined. NP exacerbated mite
allergen-induced ADSLs according to dose. OP and BP also significantly exacerbated skin lesions but not as a function of dose. Alkylphenols tended to increase the levels of
IgE and
antigen-specific
IgG1 in serum. Further, the treatment of the alkylphenols increased the expression in lesions of inflammatory
cytokines,
interleukin-4 and
monocyte chemotactic protein-3.
Thymic stromal lymphopoietin levels increased according to ADSL severity. In contrast, the levels of the T-helper 1
cytokines (interleukin-18 and interferon-gamma) decreased. NP, OP or BP may enhance T-helper 2-type immune responses in NC/Nga mice, which aggravates mite
allergen-induced ADSLs. Therefore, the uptake of very low levels of alkylphenols may contribute to the increase in the incidence of
atopic dermatitis.