PROBLEM TO BE SOLVED: To provide a pyrogenic composition and an oxygen-absorbing composition which have high initial reactivity and high moisture retainability, and can quickly generate heat or absorb oxygen on contact with oxygen.SOLUTION: A pyrogenic composition and an oxygen absorbing composition include iron powder, water and an alkali metal salt, wherein their water activity (Aw) at 25°C is 0.79 or more and 0.99 or less.