How well do you know the line-of-sight Milky Way reddening to that nearby galaxy?

Of all the contributors to dust extinction along the line of sight to an object, that coming from the Milky Way is usually expected to be the best understood. Infrared maps are commonly used to estimate the amount of dust in a particular line of sight. Similar to the previously identified excess from M82, we have searched for nearby galaxies whose infrared emission contaminates the dust maps, leading to incorrect estimates of the dust reddening. We have found about 90 galaxies in which the galaxy appears as a point source in the 100 micron IRAS images or is improperly masked. For seven sources the excess A_V is greater than 0.05 mag. M33 is shown to be oversubtracted. These galaxies are in addition to the known cases of the LMC, SMC, and M31 for which the recommended dust map values may not be correctly returned by some software packages. Accurate reddening estimates are important for measuring stellar and supernova luminosities in these nearby galaxies.