Why Pigs Can't Sweat (and Where Their Few Glands Hide)

You've probably heard someone say they're "sweating like a pig" on a hot day. Here's the irony: pigs barely sweat at all. While it's true that most of a hog's sweat glands are concentrated in its snout, lips, and feet, this fun fact misses the bigger picture—pigs have remarkably few functional sweat glands anywhere on their body.

Unlike humans, who have millions of eccrine sweat glands distributed across our skin for efficient cooling, pigs drew the short evolutionary straw. Their limited eccrine glands are confined to the snout and carpal regions (around their hooves), and these are woefully inadequate for whole-body temperature regulation. The rest of their sweat glands are apocrine glands—the kind associated with hair follicles that produce oily secretions rather than the watery sweat that cools you down.

So How Do Pigs Beat the Heat?

Since sweating isn't an option, pigs are masters of behavioral thermoregulation. This is a fancy way of saying they get creative with their cooling strategies:

• Mud wallowing: The classic pig move. Mud acts like evaporative cooling when it dries, plus it provides a protective layer against sunburn (yes, pigs can get sunburned).
• Seeking shade: Pigs will actively find cool spots to rest during the hottest parts of the day.
• Shallow breathing: They'll pant to increase evaporation from their respiratory system.
• Water immersion: Given the choice, pigs prefer clean water to mud—they're actually quite tidy animals.

The Origin of a Backwards Phrase

The expression "sweating like a pig" likely doesn't refer to the animal at all. One popular theory traces it to iron smelting. When iron ore is melted in a furnace, the molten metal is poured into sand molds called "pigs." As the metal cools and reaches a certain temperature, condensation forms on the surface—the pig "sweats." This meant the iron was cool enough to handle safely.

So next time someone says they're sweating like a pig, you can smugly inform them they're actually claiming to barely sweat at all. The real pig would be jealous of your functional sweat glands while it searches desperately for the nearest mud puddle.

Why This Matters for Pig Welfare

Understanding pigs' inability to sweat is crucial for animal welfare. Pigs are highly susceptible to heat stress, which can be fatal. Modern pig farming requires careful temperature management, adequate shade, and access to cooling systems. In factory farms where these aren't provided, pigs suffer tremendously during hot weather—all because of those missing sweat glands the rest of us take for granted.