Membrane for sht10 (humidity & temperature) sensor
The SHT1x sensors can lose calibration if exposed to excess moisture/condensation. Despite this, however, it is not meant to be damaged from excessive moisture and can even be immersed in water (see footnote 13 in datasheet).

From personal experience these sensors normally return to a calibrated state, after being left alone to dry out for 10 hours or so. 

If this still does not work you can undergo a reconditioning process. Look at the datasheet here under "Reconditioning". There is a process of baking and then re-hydrating the sensor to return it to calibration.

If the sensor is still returning spurious values after drying out for a day or so it's most likely damaged. 

You can purchase filter caps for the sensor, which are available from Farnell,  which are not supposed to effect the humidity reading. However, I've never used them personally. http://www.farnell.com/datasheets/48936.pdf