Since leather doesn't breathe, some individuals may sweat during their confinement. Depending on the amount of moisture present after use, wiping the inside of the sleepsack with a cloth may be necessary. In all cases, allowing the leather plenty of time to air-out and dry before being stored is very important, as moisture can lead to mould developing inside the sleepsack. Since leather sleepsacks can be very expensive, costing over $2,000, they must be treated with care to ensure the leather isn't damaged.