What are the downsides of sweat as a cooling mechanism?

Answer to q. 1

First and foremost, sweat means water loss. If too much water is lost, dehydration will become a very
real and immediate danger. Sweating would only evolve in organisms with regular access to potable
water. Second, sweat is only efficient in dry atmospheres where evaporation occurs at a suitable pace.
Third, sweating is most efficient on thinly-haired skin, so to be an efficient sweater means a sacrifice
of the valuable insulation that hair provides.

Answer to q. 2

The millions of nephrons within the kidneys all have delicate capillaries from which plasma is filtered.
Maintaining the correct pressure to force plasma out is essential. If the pressure is too high, there is a
good chance the capillaries will be damaged. High blood pressure from circulatory issues or diabetes
can both damage the capillaries of the kidneys.

You are really a genius. Thanks

NP