Seresto flea collar for cats: are we ignoring the nutrition variables that could change outcomes?
Every Seresto thread I’ve seen reduces to “works great/no issues” vs “never again,” with zero discussion of how diet and supplements might change efficacy, exposure, or risk. That feels like a blind spot for a nutrition-focused community.
Here are the variables I’m questioning:
Sebum-dependent distribution: These collars rely on the lipid layer of the skin to spread actives. Essential fatty acid status, zinc, biotin, and overall dietary fat can affect sebum quality and coat. Has anyone noticed differences in speed of flea control or local irritation in cats on low-fat foods, fish-oil heavy regimes, or home-cooked/raw diets with variable omega-6:omega-3 ratios?
Hepatic metabolism and supplements: Imidacloprid and flumethrin are metabolized in the liver (cytochrome P450 pathways). We routinely recommend fish oil, SAMe, milk thistle, turmeric, etc. Which of these actually induces or inhibits feline CYP enzymes and could alter systemic exposure or adverse effects with a collar that’s supposed to remain mostly cutaneous? Any pharmacology references from feline-specific data would be gold.
Grooming ingestion and diet matrix: Cats groom the collar area. If small amounts are ingested, does dietary fat level or bile flow (high-fat vs low-fat meals) change absorption of these lipophilic compounds? Any GI signs correlated with diet type when the collar is on?
Body condition and storage: Overweight cats and those with dry skin vs greasy coats-any observed differences in efficacy, residue transfer, or reactions? Are there patterns by body condition score that we’re just not tracking?
Micronutrient status and skin barrier: Deficits in EFAs, zinc, and B vitamins impair barrier function. Could a compromised barrier increase dermal penetration and local irritation from the collar actives?
Confounders we never report: environmental humidity/temperature, bathing frequency, concurrent spot-ons, and type of bedding (which might re-expose). If we don’t control for diet plus these, our anecdotes are noise.
I’ve read the incident reports and the rebuttals. What I can’t find is data that stratify outcomes by diet, supplement use, and coat/skin quality. If we’re going to keep saying “nutrition matters,” why do we treat pesticide use as diet-agnostic?
If people are willing, can we crowdsource structured observations?
- Diet type (kibble/canned/raw/home-cooked) and estimated fat percentage
- Omega-3 or other supplements (dose form and frequency)
- Coat/skin notes (dry/greasy, dandruff, pruritus baseline)
- Body condition score and age
- Any hepatic/renal history
- Time to flea control, any adverse signs (dermal/GI/neuro), and whether they resolved after collar removal
- Season, indoor/outdoor, bathing/grooming habits
I’m not looking for fearmongering or marketing claims-just mechanism-aware, nutrition-informed experiences and, ideally, citations. If anyone with a vet tox/pharm background can comment on real-world magnitude of these interactions in cats, that would move this conversation past the usual yes/no shouting match.