A flexible polyurethane foam comprising a reaction product of a reaction mixture that comprises a) an isocyanate-functional quasi-prepolymer, which isocyanate-functional quasi-prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide with an excess of an organic polyisocyanate that includes at least 80 weight-% diphenylmethane diisocyanate of which diphenylmethane diisocyanate at least 50 weight - % is 4,4'-diphenylmethane diisocyanate, wherein the isocyanate-functional quasi-prepolymer has an isocyanate content of 5 to 15% by weight and contains 30 to 70 weight percent of oxyethylene units, based on the weight of the isocyanate-functional quasi-prepolymer, b) water, c) at least one polymer polyol comprising polymer particles dispersed in at least one base polyol, d) at least one silicone surfactant and e) at least one ethylene oxide/higher alkylene oxide block copolymer, wherein i) the quasi-prepolymer constitutes 50 to 75% of the combined weights of components a-e; ii) water constitutes 15-41% of the combined weights of components a-e; iii) the at least one polymer polyol constitutes 8 to 20% of the combined weights of components a-e and the polymer particles constitute 0.5 to 8% of the combined weights of components a-e; iv) the at least one silicone surfactant constitutes 0.5 to 3% of the combined weights of components a-e and v) the at least one ethylene oxide/higher alkylene oxide block copolymer constitutes 0.5 to 3% of the combined weights of components a-e. a) an isocyanate-functional quasi-prepolymer, which isocyanate-functional quasi-prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide with an excess of an organic polyisocyanate that includes at least 80 weight-% diphenylmethane diisocyanate of which diphenylmethane diisocyanate at least 50 weight - % is 4,4'-diphenylmethane diisocyanate, wherein the isocyanate-functional quasi-prepolymer has an isocyanate content of 5 to 15% by weight and contains 30 to 70 weight percent of oxyethylene units, based on the weight of the isocyanate-functional quasi-prepolymer, b) water, c) at least one polymer polyol comprising polymer particles dispersed in at least one base polyol, d) at least one silicone surfactant and e) at least one ethylene oxide/higher alkylene oxide block copolymer, wherein i) the quasi-prepolymer constitutes 50 to 75% of the combined weights of components a-e; ii) water constitutes 15-41% of the combined weights of components a-e; iii) the at least one polymer polyol constitutes 8 to 20% of the combined weights of components a-e and the polymer particles constitute 0.5 to 8% of the combined weights of components a-e; iv) the at least one silicone surfactant constitutes 0.5 to 3% of the combined weights of components a-e and v) the at least one ethylene oxide/higher alkylene oxide block copolymer constitutes 0.5 to 3% of the combined weights of components a-e. i) the quasi-prepolymer constitutes 50 to 75% of the combined weights of components a-e; ii) water constitutes 15-41% of the combined weights of components a-e; iii) the at least one polymer polyol constitutes 8 to 20% of the combined weights of components a-e and the polymer particles constitute 0.5 to 8% of the combined weights of components a-e; iv) the at least one silicone surfactant constitutes 0.5 to 3% of the combined weights of components a-e and v) the at least one ethylene oxide/higher alkylene oxide block copolymer constitutes 0.5 to 3% of the combined weights of components a-e.