Two top-rated sensitive stomach formulas, compared side-by-side on ingredients, AAFCO compliance, recall history, and aggregated verified-buyer outcomes. Here's the honest breakdown.
On a side-by-side ingredient and outcome analysis, Purina Pro Plan edges out Hill's by a slim margin. Better protein source (real salmon vs chicken meal), live probiotics, and a lower price point — and verified-buyer reviews for chronic-GI dogs skew slightly more positive. That said, Hill's wins for dogs allergic to fish.
Salmon & Rice · 30 lb
Real salmon as #1 ingredient, live probiotics, prebiotic fiber. Most veterinarian-recommended.
Chicken Recipe · 30 lb
Chicken-based, prebiotic fiber, vitamin E. Backed by 220+ vets. Read our full Hill's review →
| Specification | Purina Pro Plan | Hill's Science Diet |
|---|---|---|
| First Ingredient | Real Salmon WINNER | Chicken Meal |
| Protein % | 26% WINNER | 22% |
| Fat % | 16% | 14% |
| Fiber % | 4% max | 5% max |
| Live Probiotics | ✓ Yes WINNER | Prebiotics only |
| Omega-6 Fatty Acids | 2.6% | 3.0% WINNER |
| AAFCO Statement | All Life Stages | Adult Maintenance |
| Price (30 lb, approx.) | ~$75 CHEAPER | ~$79 |
| Auto-Ship | Available on Chewy WINNER | Available |
| Verified-Buyer Rating | 4.8 / 5 (8,910 reviews) WINNER | 4.6 / 5 (6,400+ reviews) |
| Best For | Most dogs, value seekers | Dogs allergic to fish |
Real salmon beats chicken meal for digestibility
Typically a few dollars cheaper, plus Chewy Auto-Ship savings
Backed by 220+ vets, decades of clinical use
Higher omega-6 + vitamin E for skin support
Chicken-based, no fish
Live probiotics in every bag
On paper these formulas look similar — both are AAFCO-compliant, both target sensitive stomachs, both are easy to find. But three differences decide which one is right for your dog.
Purina Pro Plan leads with real salmon as its first ingredient. Hill's leads with chicken meal. Neither is "bad," but they behave differently for sensitive dogs. Salmon is a novel-ish protein for most dogs and naturally carries omega-3 fatty acids that support both gut lining and coat. Chicken is one of the most common canine food allergens — so if your dog has reacted to chicken-based foods before, Hill's chicken recipe is the wrong starting point and Pro Plan's salmon formula is the safer bet. Chicken meal itself is a concentrated, rendered protein (more protein per gram than fresh chicken), which is why Hill's still hits solid protein numbers despite the lower headline percentage.
This is the most practically important difference for chronic loose stools. Pro Plan guarantees live probiotics (beneficial bacteria) in every bag through its expiration date. Hill's uses prebiotic fiber — food that feeds the bacteria already in your dog's gut, but no live cultures. For a dog whose microbiome is already disrupted (after antibiotics, illness, or a long run of soft stools), live probiotics tend to help re-seed the gut faster. For maintenance in an otherwise-stable dog, prebiotics are often enough.
Hill's runs slightly higher fiber (5% vs 4%) and lower fat (14% vs 16%). Higher fiber can firm up stools and is gentler for dogs prone to loose movements; lower fat is easier on dogs with a history of pancreatitis or fat sensitivity. Pro Plan's higher fat delivers more calories and palatability, which matters for picky eaters or dogs that need to keep weight on. Hill's edges ahead on omega-6 (3.0% vs 2.6%) plus added vitamin E, which is why it's the stronger pick when skin and coat are the main complaint rather than digestion.
If you want a single rule of thumb, use this:
Across aggregated verified-buyer reviews on Chewy and Amazon — filtered to buyers who explicitly mention chronic GI issues, vomiting, or loose stools — a few patterns recur for both foods:
These are summary patterns from publicly visible verified-buyer reviews — we never reproduce an individual customer's words as a direct quote. See the full Purina review and Hill's review for per-product source links.
Whichever you pick, the fastest way to cause the vomiting and diarrhea you're trying to fix is to swap foods overnight. Transition over 7–10 days: start at roughly 25% new food / 75% old for three days, move to 50/50 for three days, then 75/25 for three days, and finally 100% new food. If stools soften at any stage, hold at the previous ratio for a few extra days before advancing. Dogs with very reactive stomachs may need a full two weeks. Our symptom guide covers the transition plan in more detail.
For active loose stools, Purina Pro Plan's live probiotics give it a slight edge because they help re-establish gut bacteria. If diarrhea lasts more than 48 hours, is bloody, or comes with lethargy, see a vet before changing food.
It's not recommended long-term. Mixing two different formulas makes it impossible to tell which one is helping or causing a reaction. Pick one, run a full transition, and judge it over 4–6 weeks.
Purina Pro Plan is usually a few dollars less per 30 lb bag, and Chewy's Auto-Ship typically lowers the per-bag cost further. Hill's is priced at a slight premium tied to its veterinary brand positioning.
No. Both are over-the-counter sensitive-stomach formulas you can buy without a vet's authorization. For severe cases, a vet may instead prescribe a therapeutic GI diet such as Hill's i/d or Royal Canin Gastrointestinal.
Start with Purina Pro Plan — it's better value, has real salmon, includes probiotics, and works for the most dogs. Switch to Hill's only if your dog is allergic to fish, or if you've tried Pro Plan for 4-6 weeks without improvement.
Check price on Pro Plan →Prices and review counts are approximate and shift over time; figures last checked June 2026.