Tackle a "routine" cleaning issue first. To clean a cowhide rug, you have a couple of options. You may use a soft-bristle brush attachment on your vacuum cleaner and gently vacuum, going with the grain of hair. In other words, do not push the hairs up when vacuuming. This process may be time consuming, but it will collect any settled dust without picking up the rug each time.
If you prefer the old-fashioned method and have help, simply pick up your rug at each of the four corners, fold in half. Carry your cowhide rug outside and gentle shake loose any dust that has collected in your rug. "Shaking" cowhide rugs seems to give them a chance to breathe and it also offers an opportunity to clean underneath them. However, cowhide hides are typically heavy and this method is best used only when two or more people are available to move the rug around.
If you have a spill on your cowhide rug, do not panic, it is still simple to clean. Take a damp cloth and a squirt of dish soap on your cloth and gently stroke with the grain of hair. Remove all of the spill with your cloth; once the spill is cleaned, rinse your cloth until it runs clean. Go over your spill several times until all soap is removed. Place a couple of books or other object underneath the area of the spill to allow for air drying. The drying process should take no more than 24 hours, depending on the humidity in the room.
Never "dry clean" a cowhide rug. There is no need for such a process. If dust mites are an issue, simply vacuum your rug instead of shaking it out to prevent any build up of mites or other allergens.