# Why is my bruise warm? **URL:** \ **Category:** Factual Questions\ **Created:** [February 4, 2007, 9:14pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825 "2007-02-04T21:14:21Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [February 4, 2007, 9:14pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/1 "2007-02-04T21:14:21Z")
Why is my bruise warm. I have a bruise on my butt about the size of my hand. The surrounding area (leg, rest of butt, back, abdomen) is relatively cool to the touch, but the bruise is very warm. Why is this? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 4, 2007, 9:40pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/2 "2007-02-04T21:40:35Z")
Basically, blood flow. Most types of injuries cause local capillaries to open up in order to deliver more blood to the injured area, since it requires more nutrients and oxygen to speed healing. Since there’s more blood flow, the area feels warmer. You’ll notice it more on parts of the body more sensitive to heat, like the cheeks (both pairs). ---
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [February 4, 2007, 10:45pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/3 "2007-02-04T22:45:34Z")
[QUOTE=Q.E.D.] Basically, blood flow. Most types of injuries cause local capillaries to open up in order to deliver more blood to the injured area, since it requires more nutrients and oxygen to speed healing. Since there’s more blood flow, the area feels warmer. You’ll notice it more on parts of the body more sensitive to heat, like the cheeks (both pairs). [/QUOTE] Nifty. Thanks for a really good answer. Capillary drool – I guess that increase in blood flowing in must also account for much of the swelling. ---
**Author:** ![AuntiePam](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@AuntiePam](https://boards.straightdope.com/u/AuntiePam)\ **Post date:** [February 4, 2007, 10:59pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/4 "2007-02-04T22:59:55Z")
When my broken hip was healing (repaired by surgery), my thigh was warm all the time. I kinda miss the extra warmth, now that it’s healed. But I guess that’s what lap cats are for. 🙂 ---
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [February 4, 2007, 11:45pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/5 "2007-02-04T23:45:07Z")
[QUOTE=AuntiePam] When my broken hip was healing (repaired by surgery), my thigh was warm all the time. I kinda miss the extra warmth, now that it’s healed. But I guess that’s what lap cats are for. 🙂 [/QUOTE] It was my cat, [Buddy](http://my.tbaytel.net/culpeper/DragonsOfHopeUniform.jpg), who made me notice the warmth. He kept trying to snuggle up to my bruise, which being a little painful, was not OK with me. (Eventually, I had to lock him out of my room for the night, which left me feeling guilty.) I was wondering why the heck he kept trying to do this. It was somewhat cool in my house (the outside temp dropped below -30C overnight, and the furnace took a while to catch up), so I figured Buddy was looking for something warm. I tried placing my palm on the bruise, and sure enough, it was quite a bit warmer than the rest of me. Being the curious fellow that I am, that set me to wondering why the buise was so warm. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [February 5, 2007, 4:22am UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/6 "2007-02-05T04:22:11Z")
Being the curious fellows that we am, do you think you’re going to get out of this thread without explaining how you got a bruise on your nether regions? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [February 5, 2007, 6:18am UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/7 "2007-02-05T06:18:59Z")
[QUOTE=Muffin] Capillary drool – I guess that increase in blood flowing in must also account for much of the swelling. [/QUOTE] Not directly. The swelling is caused by two other processes. One is that the cappilaries have been torn open and are leaking fluid directly into the surrounding tissues. The other factor is that the hormones released in reposnse to the damage have made the cappilaries more permeable to allow greater materials exchange with the damaged area. The effect is that fluid is lekaing into the tissues causing swelling. The swelling form those processes would occur even if the cappilaries weren’t dilated. ---
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [February 5, 2007, 11:58am UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/8 "2007-02-05T11:58:43Z")
Thanks, **Blake**. That’s fascinting! ---
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [February 5, 2007, 12:10pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/9 "2007-02-05T12:10:48Z")
[QUOTE=Northern Piper] Being the curious fellows that we am, do you think you’re going to get out of this thread without explaining how you got a bruise on your nether regions? [/QUOTE] I’d like to be able to say that it was a result of a night of rough sex with my coffee klatch, but the reality is much more mundane – a face plant while skiing – muffed a slight sped check before going off a lip, resulting in my landing off balance and bouncing forward from my skis onto my shoulder – rolled OK, but was slow in tucking up my legs in the roll, resulting in them levering over and whapping down on the ice, givng me a bruise on the hip side of my butt. All in all, I would much have preferred the coffee klatch scenario, but one can always hope. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [February 5, 2007, 3:32pm UTC](https://boards.straightdope.com/t/why-is-my-bruise-warm/390825/10 "2007-02-05T15:32:47Z")
[QUOTE=Muffin] Nifty. Thanks for a really good answer. Capillary drool – I guess that increase in blood flowing in must also account for much of the swelling. [/QUOTE] It was the ancient Greeks, IIRC, that set out the four signs of inflammation: dolor (pain), calor (heat), rubor (redness), and turgor (swelling).