Cat treats for sensitive stomachs — single protein

Three treat types causing loose stools is a real pattern — it usually means something common across those products is the culprit, whether that's a mixed protein base, a filler, or an additive like glycerin or yeast. Cats are notoriously fussy eaters for good reason: they tend to do best with strongly-scented, meat-based treats and often reject or react badly to anything sweet or grain-heavy. The best options for sensitive cats are high-protein and stripped back to as few ingredients as possible. To point you in the right direction — is this mainly about rewarding your Chartreux, or are you also using treats for training or enrichment? And do you have any sense of which protein sources have caused trouble so far?

That's a really useful distinction. The fact that even a chicken-only treat caused issues when it was loaded with additives strongly suggests the chicken itself may not be the problem — it's more likely something in the processing: glycerin, natural flavourings, added vitamins in high doses, or preservatives. Before ruling out chicken entirely, it's worth trying a genuinely clean single-protein source. What were the additives like on the one that was chicken-only — do you still have the packet, or do you remember anything listed on it?

Glycerin is a frequent offender for loose stools in cats — it's a humectant used to keep soft treats moist, and some cats simply can't tolerate it. Added flavourings are another wildcard. What you need is something where the entire ingredient list is one item. I'd go with Natures Menu Pure Freeze-Dried Chicken Cat Treats. The ingredient list is literally: chicken. Nothing else. The freeze-drying process preserves the scent and flavour intensely, which matters a lot for an older cat whose appetite can become more selective with age. They're small, low-calorie, and ideal for a less active 10-year-old. If he reacts to these too, then chicken genuinely is the issue and you'd move to a novel protein like duck or venison — but I'd try this first given the evidence is pointing at additives rather than the protein itself.

Yes, freeze-dried treats are generally very well tolerated by older cats — in some ways better than conventional treats because there's no heat processing that degrades proteins, and no need for the preservatives or humectants that cause problems. The one thing to be aware of is that freeze-dried raw technically carries a slightly higher bacterial load than cooked, though for a healthy 10-year-old with no immune issues it's not a meaningful concern. If you wanted to be extra cautious, Natures Menu also do a cooked, air-dried chicken treat range that's similarly minimal on ingredients. But the freeze-dried version is my first pick here given what's been causing trouble.

Good luck — I hope he takes to them. If his stomach is happy after a week or two, you'll have confirmed it was the additives all along, which at least means you have options going forward. If you do hit another issue, come back and we can look at a novel protein route.