Can an allergy/intolerance/IBS just suddenly turn up?

[FishWithABicycle]

Do conditions like allergies, intolerances and IBS develop gradually or can symptoms just suddenly present themselves in previously healthy individuals?

40yo vegetarian, somewhat overweight (no idea what I weigh but I wear size 22). I've been trying to improve my health over the last couple of months doing more regular exercise and was doing the 5:2 ish (no problem with having 2 days a week low/zero food but wasn't really being calorie controlled on the other 5 days so wasn't getting noticeably thinner)

My digestion has been misbehaving for over a week and I initially thought it was a mild bout of enteritis but as I was feeling otherwise healthy and getting hungry I stopped trying to starve it out as I would with something like that. However symptoms are continuing (tmi alert sorry for being graphic) I'm talking sloppy smelly too-frequent poo but not quite diarrhea.

Googling suggests it sounds like IBS or a food intolerance but I hadn't thought something like that could just develop suddenly. I'm going to try eating a low FODMAPS diet to see if that improves things but I'm worried about this as I tend to get severe depression when on a restricted diet and I don't want my mental health to deteriorate for the sake of my physical health.

I'd be interested to know whether a sudden onset like this has happened in anyone else out there?

I'd also like to know how long I should give the low FODMAPS diet to see if it works (i.e. how quickly would you expect to see an improvement?)

If low FODMAPS does improve things do I just stick to that for a period (how long?) then start experimenting with the foods-to-avoid list to see what I can tolerate?

If it doesn't help, how long do I wait before giving up and what do I try next?

You should see a GP to exclude anything serious. Peppermint oil may settle things a bit, but if not, it will defo make the loo space more pleasant for anyone else that shares it with you. Tummy issues can be allergy related, but are often stress related too. Takes long warm baths, relax, and see a GP to exclude anything serious. A bug can take around 21 days to lose its grip.

bumping this as I'm in a similar situation.

yup, i developed IBS aged 22 during a very stressful year. There are a few foods that make it worse, but its still mainly stress or exhaustion so if going on a restricted diet would affect your mental health then i wouldnt, personally. See your doc and rule anything else out - lactose intolerance, for example, can develop after a big stomach upset, but if it is IBS its a lot about figuring out what works for you. I find probiotics helpful, no coffee, alcohol, insoluble fibres, and managing my stress

Yes in my experience, i'm having various issues at the moment but they've been going on and off for nearly a year now. I've had various blood tests but at my appointment this week it was suggested I now look into fodmap and if this doesn't work after 6 weeks or so to come back for a coeliac test.

I find keeping a food diary helps a bit as it can help pin point food that is aggrivating you and when I do get a flare up peppermint oil in warm water is the best remedy.

Yep. I discovered I had Coeliac disease at 49. Had no real symptoms until then, it had lain dormant I guess.

Yes in my experience. I developed IBS in chilhood & figured out in late teens I'm irritated by a whole host of foods which set it off. I mostly try to avoid the worst ones by my diet would be incredibly dull and I'd probably end up malnourished if I avoided them all. I have 1 serious food allergy (thankfully not a common food) & have recently started excluding milk as I suspect allergy/intolerance, I feel masses better. I'm mid 30s.