(Oxidation reaction of oxidizable metal powder to proceed smoothly to achieve good temperature rise characteristics (heat generation rise characteristics), good heat generation performance such as long-term persistence (exothermic sustainability) of exothermic temperature, It is an object of the present invention to provide an exothermic composition which is easy to manufacture, does not become bulky at the time of use, is easy to use, and is excellent in economic efficiency, and a disposable warmer using the exothermic composition. An exothermic composition containing an oxidizable metal powder, an inorganic electrolyte, water, a carbon component and a water retention agent and generating heat in the presence of air, wherein the carbon component is a conductive carbon material having an average particle diameter of 10 to 100 nm , And its content is such that the exothermic effective surface area per 1 g of the exothermic composition is 0.8 m2Or more, and is used in an amount of 7 mass% or less with respect to the entire exothermic composition.被酸化性金属粉の酸化反応をスムーズに進行させることによって良好な昇温特性(発熱立上り特性)を達成させ、発熱温度の長期間の持続性(発熱持続性)等の発熱性能が良好で、製造が容易で、使用時に嵩張ることがなく、使い勝手がよく、経済性にも優れた発熱組成物と、それを使用した使い捨てカイロの提供をすることを課題とする。被酸化性金属粉末、無機電解質、水、炭素成分および保水剤を含有し、空気の存在下で発熱する発熱組成物であって、前記炭素成分は、平均粒径10~100nmの導電性炭素物質で、その含有量は、発熱組成物1g当たりの発熱有効表面積が0.8m2以上で、かつ前記発熱組成物全体に対して、7質量%以下の量で用いる。
