Abstract: The invention relates to model systems for allergic conditions, and in particular to in vivo model systems in a large animal. The model systems of the invention are especially useful for providing large numbers of activated or non-activated eosinophils, for the discovery and evaluation of novel anti-inflammatory drug targets and for providing a model for the in vivo study of asthma and the effects of allergy treatments. In a preferred embodiment the animal is a sheep. In one embodiment, repeated infusion of house dust mite allergen (HDM) into the mammary gland is used to induce a specific allergic response, which is characterised by the recruitment of inflammatory cells, particularly eosinophils, into the mammary lumen; these cells can be harvested from peripheral blood and mammary lavage (MAL).