On Shabbos, if a baby is born during the 8th month of pregnancy, we no longer hold the baby is muktzah. The reasoning is either:
1) Halacha Changes
2) Situations Change
3) Nature Changes

If so, what's with showering during the 9 days?
1) Halacha changes? Not so easy.
2) Situations? Very easy. We no longer only shower once a week at a maximum and so not showering for the 9 days is too much.
3) Nature? Well, not really, but we are different. We get disgusted instinctively when we discuss not showering for 9 days.

So, what say you?

in this insane heat, if you start smelling like a homeless person, i say PLEASE SHOWER!!
While I'm generally not a shower fanatic and can go a couple of days without one, I had a dr's appt yesterday morning and there was no way i was gonna show up there reekin' away. So know your boundaries and guidelines - shower without soap or little soap, but if youre takin' someones breath away, puleez wash yourrself. no, not every day, and not if youre 'uncomfortable' - only if youre a'smellin'.

And hey this is not a psak. I'm not an ordained rabbi. Just an opinion.

My understanding is today we have the din of an istanus, a delicate person. This is probably only in the last 100-150 years btw, when indoor plumbing made frequent bathing easy.
From my rav, my understanding is to take showers in colder water than normal. And if you are actually dirty/sweaty then there shouldnt be an issue at all. It is a question of bathing for pleasure.

You'd be surprised...I know a few people who wouldn't blink at the thought. *shudder*

Eh, what have you got against us homeless people ?

I haven't showered in the past 3 years. So?

you are more than welcome to use ours. We have plenty of hot water and clean towels. I would be more than happy to allow you to use ours assuming you have a problem b/c of living conditions that do not include a shower.

But it might ruin my circuits!!

The criteria for showering during the nine days, as I understand it
1. less comfortable than normal
2.not the whole body at once
3.not for pleasure ("mmm great shower") but just to get clean body parts.

People used to bathe once a week. Not bathing for the nine days didn't mean as much to them. People today shower even during shiva. It is a completely different cleanliness scale today. If you are used to showering ever day or more then showering every 2-3 days when you feel disgusting and alternating body parts you wash, etc, is enough to be fulfilling the mourning of the nine days. As far as I learned.

Can anyone define istenis?

We may be more sensitive to certain things than people generally were 100 years ago, but maybe it doesn't yet qualify as istenis? Istenis is described as a person who has no enjoyment from this world. Are your negative feelings really that intense? True, you don't like to skip showers, but do you suffer on a daily basis from other sensitivities? As different people have their personal sensitivity line, could istenis be another name for Sensory Integration Disorder or the like?

For those interested in the halachic issues involved, see Harerei Kedem 2:139 (be'inyan rechitzah betzoinen be'tishas ha'yamim).
Basically he says that the Rama (OC 551:16)who holds that you cant even take a cold shower only holds that because the 9 days has the din of shloshim, and the Rama holds by shloshim (YD 381) that you cant take a cold shower. But the Shach (SK 1) holds that you are allowed to take a cold shower during the shloshim, and thats he we are noheg, so therefore it should be mutar to take a cold shower during the 9 days.
However, at the end he shows that this explanation appears to be the subject of a machlokes achronim.

Thank G-d we're discussing this online.

I wouldn't want to be smelling this live.

Anyways my rov told me that since in today's age it is the norm to take a shower every day, people have more sensitive skin and therefore not showering for 9 days will lead to skin ailments. Which if you want to really FEEL the pain of the nine days, you're more than welcome but there's no halachic obligation.

But that's why we have erev Shabbos!

And how about wearing clean clothes...?

For those who claim the leniency to ignore halachah is based on an extrapolation of the laws of istnis: Where in hilchot aveilut is there a leniency for an istnis? And do aveilim, r"l, break out in suppurating purulent skin discharges or even rashes from not showering? Or are we picking and choosing to ignore an halachah that makes us uncomfortable and embarassed among others?

Mishna Brachos 16b, Rabban Gamliel bathed at night after his wife's funeral.
Rashi classifies istenis as adam meunag u'mefunak, which is not a stretch for most people today.