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<h4>Background</h4>Aging may be accompanied by a low grade chronic up-regulation of inflammatory mediators. A variety of endogenous locally released mediators as well as inflammatory cells have been reported in the human oral cavity. The aim of this investigation was to determine the presence of different classes of inflammatory mediators in human saliva and correlate the levels with age.<h4>Methodology and principal findings</h4>Unstimulated whole buccal salivary samples were obtained in the morning from 94 healthy volunteers within 30 minutes after waking. None of the participants had taken aspirin in the week prior to the saliva collection. Lysozyme activity, eicosanoid levels (prostaglandin E(2) and leukotriene B(4)) and MMP-9 activity were measured. The antimicrobial activity (lysozyme activity) was not correlated with age whereas PGE(2) levels were markedly correlated with age (r = 0.29; P<0.05; n = 56). Saliva from healthy subjects (< or =40 years) compared with data derived from older volunteers (>40 years) demonstrated a significant increase in the mean values for PGE(2) and MMP-9 activity with age. In addition, significant correlations were observed between LTB(4) and PGE(2) (r = 0.28; P<0.05; n = 56) and between LTB(4) levels and MMP-9 activity in smokers (r = 0.78; P<0.001; n = 15).<h4>Conclusions/significance</h4>The presence of significant levels and activity of inflammatory mediators in saliva suggests that the oral cavity of healthy subjects may be in a constant low state of inflammation associated with age.