The effects of systemic inflammation on the pathogenesis of Alzheimer's disease (AD) are not clarified, both beneficial and deleterious effects being reported . Allergy is accompanied by a systemic inflammatory response and some epidemiological studies have reported a positive association between a history of allergy/asthma and dementia . To investigate whether chronic airway allergy influences the inflammatory status in the brain, AD-like pathology, and behaviour in relation to AD, we induced chronic airway allergy in triple transgenic AD (3xTgAD) and wildtype (WT) mice by repeated exposure to ovalbumin (OVA) as allergen . Behavioural tests relevant for hippocampus-dependent behaviour were performed . We found that allergy significantly increased the brain levels of immunoglobulin (Ig) G, IgE . In 3xTgAD mice, allergy increased the levels of decay accelerating factor and decreased the phosphorylation of p38 . In contrast, allergy increased the levels of interleukin (IL) -1ß and complement component 1q (C1q) in WT mice . Bronchoalveolar lavage fluid analysis confirmed eosinophilia in both genotypes, but the basal levels of eosinophils were lower in 3xTgAD mice . In summary, allergy induced predominantly anti-inflammatory effects in 3xTgAD mice, and pro-inflammatory effects in WT mice, thus being another potential factor to be considered when studying AD pathogenesis.