1. An absorbent article that includes: a substantially liquid impermeable layer； a liquid permeable layer； an absorbent internal structure located between the substantially liquid impermeable layer and the liquid permeable layer； a moisture sensor integrated in the product and installed in such a way that the sensor is in fluid connection with physiological fluid coming from the user of the product； wherein the humidity sensor contains ink comprising a proton-acceptor chromogen and a proton donor agent, where the proton donor agent includes an aliphatic carboxylic acid； while the color of the ink undergoes a visible change in contact with physiological fluid. 2. The absorbent article of claim 1, wherein the solubility of the aliphatic carboxylic acid in water is more than about 5 g per 100 ml of water at a temperature of 20 ° C3. The absorbent article of claim 1, wherein the first acid dissociation constant of the aliphatic carboxylic acid is from about 0 to about 8.4. An absorbent article according to claim 1, wherein the humidity sensor is located on a substantially liquid-impermeable layer. The absorbent article of claim 1, wherein the humidity sensor further includes a substrate on which ink is applied, the substrate being integral with the absorbent article. The absorbent article of claim 1, wherein the proton-acceptor chromogen is a leuco dye that is usually colorless in a deprotonated state. The absorbent article of claim 6, wherein the leuco dye includes phthalide, phthalene, acyl-leukomethylene, fluoran, spiropyran,1. Абсорбирующее изделие, которое включает:по существу непроницаемый для жидкости слой；проницаемый для жидкости слой；абсорбирующая внутренняя структура, расположенная между по существу непроницаемым для жидкости слоем и проницаемым для жидкости слоем； идатчик влажности, встроенный в изделие и установленный таким образом, что датчик находится в жидкостном соединении с физиологической жидкостью, поступающей от пользователя изделия； при этом датчик
