Oat is considered as one of food raw materials of high nutritional value. Its proteins are characterised by very high content of globulins rich in exogenous amino acids as compared to other cereal proteins. In spite of the positive nutritional aspects, the oat consumption can result in some human health threats, as oat proteins have been demonstrated to be able to cross react with wheat anti-gliadin polyclonal antibodies. The aim of this work was to determine the cross reactivity between Ara h1 allergen present in peanuts (Arachis hypogaea) and proteins of oat grains. The cross reactivity of oat proteins with Ara h1 allergen was determined with the use of RIDASCREEN Peanut test. In our study, it was shown that within oat protein structures there are hidden similar determinants immunologically comparable to those found in Ara h1 allergen, and temperature appears to be a very important factor which can affect their revealing and thus increase their availability to anti–Ara h1 allergen antibodies.