Ha! 
It’s a good thought. But for better or for worse we don’t have a cat (I’m allergic) and our daughters are long out of diapers…
But to be honest, I’m still not sure it’s my breath. It could be sweat, could be something else. Part of me still feels like it’s my sense of smell. Next time I notice it, I’ll make sure I breathe all over my daughters and ask them to smell my breath. They love it when I do stuff like that… 
I have experienced the same thing (actually for many years now). I believe my diet is solid, and that I’m well hydrated. I used to notice this happen after hard 45 minute runs on the treadmill in the morning (years ago). Never could figure out what the smell came from . I always thought it was my sweat. I’ve noticed it happen here and there after TR workouts. FYI, 90% of my workouts are done first thing in the morning with only about a half cup of black coffee in my stomach. I eat after. If I have a SS workout longer than 1 hour I will consume a gel and put skratch in my bottle. Interested in this thread for sure.
Along those same lines @amcananey and @oldcrank are you sure it’s not something like your bar of soap (maybe as it’s mixing with your sweat) you’re smelling?
I used to think I was noticing same thing and had similar concerns. Then I realized it was actually the soap smell (some flavor of Dove I think) that was just getting stronger when washing off lots of sweat.
Smell your soap!
@dbf The smell isn’t like my soap (I thought it might have been my shampoo) usually smells. And after one of these incidents, I’ve gone back a few hours later to re-smell my soap and shampoo and I didn’t notice the same smell. More recently, I noticed the same scent after a workout when I wasn’t showering. It wasn’t as intense, and it went away faster, but it was definitely there.
In any case, I feel fine, no aches, and my workouts aren’t suffering in any way, so I’m going to assume it’s OK and I can just carry on until someone knowledgeable here tells me otherwise! 
This is an interesting thread. I don’t know if what I experience is the same thing, but after challenging workouts I get a chemical smell. It’s usually right after I’m done and lasts for 10-15 minutes. I thought (think?) it’s my body/sweat reacting with my kit, but maybe not. I don’t think it’s ammonia. I don’t know what acetone smells like. I am generally well-fueled, definitely don’t skimp on my carbs, and try to hydrate well. The smell isn’t always there after a tough workout, but it shows up from time to time.
I’m relatively new to cycling, but not new to challenging workouts. I am new to lycra though, so I thought it might be that 
At least I’m glad I’m not alone.
Been there done that! I was high protein low carb. My workouts were fine, but I started noticing the ammonia smell. Talked to a doc who I also trained with, he said if your sweat is smelling of ammonia, then your body does not have enough carbs and has switched to protein metabolism. Liver cannot handle it all, so some goes out in your sweat. I upped my carb intake. No more ammonia.
You may be eating carbs, but are you eating enough for the volume of training you are doing?
This made me laugh out loud. Hard. A theory not to be dismissed!!!
Overall? Absolutely. I’m a fake vegan (insofar as I eat fish, but no meat or dairy products), so to be honest, most of my diet is carbs. (And note that – if anything – I smelled this scent significantly MORE often before I started trying to lose weight. In fact, I’ve only smelled it once in the past couple of weeks.)
I’m going to put this down to the digestion of dietary protein. Seems unusual, but I don’t know how else to explain it and I feel great, so I’m having trouble believing there is anything seriously wrong. I’m even having trouble believing that I’m fully depleting my glycogen reserves during my workouts, since I don’t feel like I’m hitting any kind of wall at all. I’m able to finish my workouts pretty strong with no unusual changes in effort (i.e., that aren’t explained by changes in the prescribed workload).
I’ve just started reading “Feed Zone Portables”, by Biju Thomas and Allen Lim. There is an excellent ~60 page introductory section explaining a lot of the science behind sport nutrition. In it, they write:
“If you’ve ever reached a point during long-term exercise where you begin to smell ammonia in your sweat or urine, then you’ve actually pushed yourself to a point where you’re breaking down protein and using it as a fuel source. Hitting this ‘ammonia’ threshold is extremely rare and almost never occurs if a person is eating enough carbohydrate. To be able to push yourself to this point requires an incredible level of fitness and drive – most people will quit before they reach this point.”
Based on that description, I’m confident that isn’t what I was experiencing. I am not incredibly fit and I didn’t feel like I was pushing myself to the extreme.
I have to agree. I’m fit, but for sure not incredibly fit (someday…). But the smell is unmistakable. I have noticed it after a workout, but before I’m even near a shower (so not soap, etc.). I don’t eat a “lot” of carbs though. I eat good carbs in moderate amounts (macros approximately 50 25 25). Must be my diet?
I know it is off-topic but Jethro Tull’s Locomotive Breath popped into my head as a result of reading this thread.
Next time it happens try to record as much detail from the day that you can. Like what you ate, estimates on calories burned, etc. See if we can find some commonalities to figure out what it is. Time of day, how rested you are, if you also lifted weights that day…
Will do!
I notice this every few weeks, and today was a really clear example that just doesn’t seem to fit with the undernourishment / low carb thing. Some strength training, then breakfast was muesli and half a banana. Lunch was basically pure carbs - fast and slow - wholemeal barley waffles with jam. I ate as much as I comfortably could in preparation for my TR workout, which I started 3 hours after lunch. Threshold workout - which often nearly kill me, but today’s was ALMOST EASY! The most manageable workout I’ve done for at least a couple of weeks. No problem at all completing any of the intervals or the ride as a whole. Recovery drink (SIS Rego) during cooldown, then while I’m stretching afterwards I detect a whiff of something chemical (ammonia, I think) on my breath.
What gives?
All this time I’ve honestly thought my cat pissed in my cycling shoes! They took on a strong ammonia smell last summer, when I was doing a lot of fasted rides, and 100-150 mile rides every week. The century+ rides were all fuelled of course, but you can’t ever really fuel enough for those, and always end up catabolic at some point. I guess it built up to the point of being very noticeable in the shoes after enough of those rides. Now I feel bad for banning the cat from the pain cave…
Don’t.
I get an ammonia smell in my kit after crazy hard long rides, definitely is related to overdoing it for me. I think it’s got to be due to protein breakdown of some type. How long and hard a these workouts?
+1
I wouldn’t class myself as especially fit - but I have experienced the same smell on my kit after some long strenuous club rides. Pretty sure its the protein breakdown process.
Amazing! I’ve noticed this on occasion when I jump in the shower after a training ride, I always had it in my head that somehow my sense of smell had been heightened and I was getting a whiff off the bathroom/tile cleaner or something similar to that. Never thought to link it to an internal process like depleted glycogen stores.
I guess on or around the bike I never notice it because of the fans, but in the shower the air hangs around a bit more.
Deliberately increased carbs earlier in the day, and just before my last workout yesterday and no smell— will keep an eye on it now I know to identify it.
Bumping this old topic because I have a similar question -
I am relatively new to interval training and cycling in general (~1 year TR, ~1.5 years cycling). I have noticed that it seems like I get the ammonia smell in my nose during my TR workouts almost every time. After reading some of the posts above I tried upping my carb intake prior to rides. One day recently where I tracked intake, I ate ~250g of carbs during the day prior to my 1 hr sweet spot effort with about 50g coming 3 hours before my ride. I also drank 20g of carbs from skratch mix during the ride. Once I got to the intervals I still got the familiar chemical smell in my nose.
Am I way under with how many carbs I should be eating to fuel these rides? Any other ideas? Thanks!