From the first once-yearly injectable approved in 2025 to time-tested collars, chews, and topicals — every durable flea prevention option your vet may recommend, explained with FDA-sourced facts.
A single adult flea can lay up to 50 eggs per day, and the flea life cycle lasts up to 12 weeks — which is exactly why monthly treatments can leave dangerous coverage gaps. The landscape of long-lasting flea protection changed significantly in July 2025 when the FDA approved Bravecto Quantum, the first-ever single-dose injection that protects dogs for up to 12 months. For pet owners managing complex medication schedules, mobility challenges, or simply wanting fewer trips to the pharmacy, understanding which products last the longest — and which are safest for your specific dog — is more important than ever.
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What is the longest-lasting flea protection available for dogs? Bravecto Quantum (FDA-approved July 2025) — a single injectable dose that protects against fleas for 12 months. It is the first and only product to achieve once-yearly systemic parasite protection.Bravecto Quantum (fluralaner extended-release injectable suspension) was approved by the FDA on July 10, 2025 and received an expanded label on March 18, 2026. It is administered as a single subcutaneous injection by a licensed veterinarian and kills adult fleas while preventing flea infestations for 12 months. The expanded March 2026 label also now covers Asian longhorned ticks and Gulf Coast ticks for 12 months, in addition to black-legged, American dog, and brown dog ticks. Lone star tick coverage lasts 8 months. In field study data, 99% effectiveness against fleas was documented at all post-treatment timepoints over 12 months. It is the first FDA-approved systemic product to offer full-year flea and tick protection from a single dose.
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What are isoxazolines and why does the FDA have a safety alert about them? Isoxazolines are the drug class used in Bravecto, NexGard, Simparica, and Credelio. The FDA issued an alert in 2018 that these products have been associated with neurologic adverse events (muscle tremors, ataxia, and seizures) in some dogs.Isoxazolines work by inhibiting GABA-gated chloride channels in the nervous systems of fleas and ticks, causing paralysis and death. The FDA considers them safe and effective for the majority of dogs but has required updated labeling to note the potential for neurologic events including tremors, loss of muscle coordination, and seizures. These events have occurred in some dogs with and without a prior history of neurological disorders. Dogs with a history of seizures, epilepsy, or any neurological condition should be discussed with a veterinarian before using any isoxazoline product. The FDA continues to monitor post-marketing adverse event reports for all isoxazoline products.
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How long does a Bravecto chew protect a dog from fleas? 12 weeks (3 months) per chew against fleas and most ticks. Lone star tick protection lasts 8 weeks. Bravecto chews are for dogs 6 months and older, weighing at least 4.4 lbs.Bravecto (fluralaner) oral chews start killing fleas within 2 hours and maintain ≥99% flea kill efficacy for 12 weeks. Because the flea life cycle lasts up to 12 weeks, a single Bravecto dose covers one complete flea life cycle — meaning it can break an infestation without the coverage gaps that monthly treatments risk. Bravecto chews require a veterinary prescription. Most commonly reported side effects include vomiting, lethargy, diarrhea, and decreased appetite. Use with caution in dogs with a history of neurological disorders, per FDA labeling.
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How long does the Seresto collar protect dogs from fleas? Up to 8 months of continuous flea and tick protection. No prescription required. Available over the counter. Effective on dogs and puppies 7 weeks and older.The Seresto collar (imidacloprid + flumethrin) uses a unique polymer matrix technology to continuously release low concentrations of two insecticides for up to 8 months. It kills existing fleas within 24 hours of application and newly contacting fleas within 2 hours after the initial 24 hours. The collar repels and kills both fleas and ticks and is waterproof. Key advantage over oral options: it is OTC (no vet prescription needed), works well for dogs that resist taking pills, and provides both kill and repellent effects. Key limitation: the active ingredients are on the collar surface, so humans — especially children — who frequently touch the collar may have incidental contact with the insecticides.
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Does flea protection need to be used year-round or just in warm months? Year-round. Fleas and ticks are active whenever temperatures are above freezing and can survive indoors in heated homes all year. The CDC and AVMA both recommend continuous, year-round parasite prevention for dogs.Contrary to widespread belief, fleas are not a seasonal-only threat. Flea pupae in carpet and furniture can remain dormant for months and emerge when conditions are favorable. A single warm day can activate ticks. Indoor dogs are not immune — fleas can hitch rides on clothing, other animals, and from yards and porches. Year-round protection is especially important for dogs in the Southeast, Southwest, and coastal regions where fleas are active every month. Even in colder climates, the time period when dogs are “unprotected” between seasonal treatments is when infestations begin. The flea life cycle includes egg, larva, pupa, and adult stages — only adult fleas are killed by most products; protecting continuously breaks the cycle.
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What is the difference between flea adulticides, IGRs, and repellents in protection products? Adulticides kill adult fleas. IGRs (insect growth regulators) prevent eggs and larvae from developing. Repellents deter fleas from landing. Long-lasting products typically combine two or more of these mechanisms.Understanding the mechanism helps you choose the right product. Pure adulticides like isoxazolines (Bravecto, NexGard, Simparica) kill adult fleas after they bite but do not repel them and do not address eggs or larvae in the environment. Products like Frontline Plus combine fipronil (adulticide) with s-methoprene (an IGR that sterilizes eggs and kills larvae), which is why they can help clear infested environments faster. The Seresto collar adds a repellent effect via flumethrin, meaning some fleas never reach biting distance. For homes with active flea infestations, using a product with IGR activity alongside an adulticide significantly accelerates clearing the environment.
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Is NexGard the same as Bravecto? How do they differ? Both are isoxazoline oral chewables, but NexGard (afoxolaner) is monthly while Bravecto (fluralaner) lasts 12 weeks. NexGard is approved for puppies 8 weeks and older; Bravecto requires 6 months minimum age.NexGard and Bravecto share the same drug class and mechanism of action but use different active molecules with different pharmacokinetic profiles, which accounts for their different duration of action. NexGard (Boehringer Ingelheim) kills fleas within 4 hours and is appropriate for puppies as young as 8 weeks old and at least 4 lbs — making it one of the most puppy-friendly prescription flea options. Bravecto lasts 3x as long per dose, reducing the number of annual treatments from 12 to 4, which many owners find easier to manage. Both carry the same FDA isoxazoline class warning regarding potential neurologic events.
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Can a dog with a history of seizures use flea prevention products? Yes — but isoxazoline oral products (Bravecto, NexGard, Simparica, Credelio) should be discussed with a veterinarian first. Alternative options like Frontline Plus, Seresto collar, or Revolution Plus may be more appropriate.The FDA specifically notes that isoxazoline products should be used with caution in dogs with a history of neurological disorders, including seizures, because these products have caused seizures in some dogs even without prior history. For dogs with known epilepsy or seizure disorders, many veterinarians will recommend alternatives from different drug classes: fipronil-based products (Frontline Plus), the Seresto collar (imidacloprid + flumethrin), spinosad (Comfortis), or selamectin (Revolution, Revolution Plus). These products do not carry the isoxazoline class warning. Discuss the specific risk profile of your dog’s condition and medication history with your veterinarian before selecting any systemic flea product.
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Which flea protection products are available without a prescription? Frontline Plus, Frontline Gold, Seresto collar, Advantage II, and K9 Advantix II are available over the counter at pet stores and online without a veterinary prescription. Most long-lasting oral products require a prescription.All isoxazoline oral products (Bravecto, NexGard, Simparica, Credelio) and Bravecto Quantum injectable require a veterinary prescription. Spinosad (Comfortis) also requires a prescription. Over-the-counter products including Frontline Plus (fipronil + s-methoprene), Seresto collar, Advantage II (imidacloprid), and K9 Advantix II (imidacloprid + permethrin + pyriproxyfen) are accessible without a vet visit. OTC products can be effective first-line options and are useful for budget-conscious pet owners, but prescription options generally offer longer duration and systemic coverage. Your veterinarian can help determine which approach is best for your dog’s health history and lifestyle.
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How quickly does flea protection start working? Bravecto chew: within 2 hours. NexGard: within 4 hours. Simparica: within 3 hours. Seresto collar: kills existing fleas within 24 hours, then 2 hours for new fleas. Frontline Plus: within 12 hours.Onset speed matters most when treating an active infestation. Oral isoxazolines are the fastest-acting systemic options, with most achieving ≥98% kill rates within 24 hours of administration. The Seresto collar takes up to 24 hours to reach full kill efficacy for existing fleas on the dog, but once established, kills new fleas within 2 hours of contact. Frontline Plus, a topical applied to the skin, takes about 12 hours to achieve meaningful kill rates. For a dog already covered in fleas, an oral product combined with a bath and environmental treatment gives the fastest relief. For ongoing prevention in a flea-free dog, any of these products maintain effective protection when administered on schedule.
Sources: FDA.gov CVM isoxazoline safety alert (updated Aug 2019; muscle tremors, ataxia, seizures; Bravecto/NexGard/Simparica/Credelio; safe and effective for majority of animals); FDA.gov CVM Bravecto Quantum approval (July 10, 2025; first long-acting flea and tick treatment; 8–12 months); Merck Animal Health press release March 18, 2026 (expanded label: Asian longhorned + Gulf Coast ticks 12 months; lone star tick 8 months); NCBI PMC “Survey of canine use and safety of isoxazoline parasiticides” (32,374 FDA reportable AEs 2013–2017; seizure rates; FDA/EMA comparison); us.bravecto.com (12-week chew; ≥99.8% flea reduction; FAD resolution; 2-hour onset; 6 months+ age); Allivet.com (Seresto 8 months; imidacloprid + flumethrin; kills within 24 hours; safe from 7 weeks); HardyPaw.com (Simparica 3 hours onset; NexGard 4 hours; Bravecto 2 hours); BudgetVetCare.com Feb 2026 (Seresto repellent effect; Bravecto no repellent; collar vs chew comparison)
Sources: FDA.gov Bravecto Quantum July 2025 approval; us.bravecto.com (12-week chew data); Allivet.com (Seresto 8-month duration); Frontline Plus official label (fipronil + s-methoprene; 30 days; 8 weeks+)
The profiles below are for educational purposes. All prescription products require a licensed veterinarian’s authorization. Even OTC products carry real risks if used incorrectly, on wrong-weight dogs, or on dogs with pre-existing conditions. Always consult your veterinarian before starting, changing, or combining flea prevention products. If your dog experiences any adverse reaction, contact your vet immediately. Report adverse events to the product manufacturer and to the FDA at FDA.gov/animal-veterinary.
Sources: FDA.gov CVM Bravecto Quantum approval July 10, 2025 (first long-acting 8–12 month injectable; fluralaner extended-release; dogs 6 months+); Merck Animal Health press release March 18, 2026 (expanded Bravecto Quantum label: Asian longhorned + Gulf Coast ticks 12 months; 0.9% seizure rate field study n=225); FDA.gov CVM isoxazoline safety alert (Bravecto/NexGard/Simparica/Credelio/Revolution Plus; neurologic events; muscle tremors, ataxia, seizures; manufacturers include Rev Plus per April 2019 update); us.bravecto.com (Bravecto chew: ≥99.8% flea kill 12 weeks; 2-hour onset; FAD resolution 86–100%; 3–6x more flea-free vs Frontline Plus; topical >99% within 24 hours, 100% at 48 hours laboratory); FDA safety-related labeling changes page (Simparica Trio expanded: tapeworm prevention via flea control; moxidectin + sarolaner + pyrantel); Allivet.com (Seresto: up to 8 months; imidacloprid + flumethrin; safe from 7 weeks; waterproof; kills within 24 hours first application, then 2 hours; safety-release mechanism); BudgetPetWorld.com (NexGard: afoxolaner; 4 hours onset; black-legged tick Lyme prevention; 8 weeks+; 4 lbs+); HardyPaw.com (Simparica: sarolaner; 3 hours onset; 35 days duration; mite coverage); Elanco/Credelio labeling (lotilaner; 8 weeks+; 4.4 lbs+; compact tablet; Credelio Plus with milbemycin); Zoetis Revolution Plus (selamectin + sarolaner; ear mites + sarcoptic mange + heartworm + hookworm + fleas + 5 ticks; 8 weeks+ 2.8 lbs+; FDA added to isoxazoline alert April 2019); Frontline Plus label (fipronil + s-methoprene; monthly 30 days; 8 weeks+; waterproof; 12-hour adult kill; no isoxazoline); K9 Advantix II label (imidacloprid + permethrin + pyriproxyfen; 7 weeks+; dog-only; permethrin fatal to cats; repels mosquitoes/biting flies)
| Product | Duration | Type | Rx? | Isoxazoline? | Age Min. |
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| Bravecto Quantum | 12 months | Injectable | Yes (vet) | Yes | 6 months |
| Seresto Collar | 8 months | Collar | No (OTC) | No | 7 weeks |
| Bravecto Chew | 12 weeks | Oral chew | Yes | Yes | 6 months |
| Bravecto Topical | 12 weeks | Topical | Yes | Yes | 6 months |
| Simparica Trio | 35 days | Oral chew | Yes | Yes | 8 weeks |
| NexGard | 30 days | Oral chew | Yes | Yes | 8 weeks |
| Credelio | 30 days | Oral tablet | Yes | Yes | 8 weeks |
| Revolution Plus | 30 days | Topical | Yes | Yes (sarolaner) | 8 weeks |
| Frontline Plus | 30 days | Topical | No (OTC) | No | 8 weeks |
| K9 Advantix II | 30 days | Topical | No (OTC) | No | 7 weeks |
⚠️ K9 Advantix II: permethrin component is FATAL to cats. All isoxazoline products carry FDA neurologic event warning — discuss with vet for dogs with seizure history. All durations are for flea protection per official labeling. Rx = prescription required from a licensed veterinarian.
The most common reason flea products appear to “stop working” is environmental reinfestation, not product failure. Only about 5% of a flea infestation lives on the dog; 95% lives in the environment as eggs, larvae, and pupae in carpet, furniture, bedding, and outdoor areas. When you treat the dog but not the environment, new fleas from the environment continuously jump back onto the dog and die, creating the appearance of an ongoing infestation. For a complete solution: treat all pets in the household simultaneously, vacuum all carpeted areas and immediately discard the bag, wash all pet bedding in hot water, and treat indoor and outdoor environments with an appropriate IGR-containing premise spray. The infestation should resolve within 3–8 weeks with consistent product use, as the egg-to-adult cycle completes and new adults emerge only to die on the treated pet. Seeing some fleas during this period is expected and does not mean the product has failed.
Bravecto Quantum is the newest and longest-lasting option, so it is natural to have questions. Ask your veterinarian these specifically: (1) Does my dog have any history of seizures or neurological symptoms? (The isoxazoline class warning applies.) (2) What were my dog’s baseline bloodwork results? (Elevated liver enzymes were noted among reported adverse events in clinical studies.) (3) What do I do if my dog has a reaction in the weeks following the injection? (Unlike a chew, you cannot stop the drug once injected.) (4) Which tick species are in my region, and does Bravecto Quantum cover them for the duration I need? (5) My dog is a breeding female — is this safe? (The safety of Bravecto Quantum in breeding dogs had not been fully established at initial approval; ask your vet for the most current guidance.) Because the product is still relatively new in the U.S. (approved July 2025), your veterinarian’s post-marketing experience with it will grow over time.
It depends on the product. Safety profiles vary significantly by formulation: Frontline Plus and Seresto collar are generally considered safe for pregnant and lactating dogs per their labels. Bravecto chew and topical: adverse events have been reported following use in breeding females; consult your veterinarian before use. Bravecto Quantum injectable: safety in breeding dogs was not fully established at initial approval — ask your vet for current guidance. NexGard, Simparica Trio, Credelio: all carry label language advising consultation with a veterinarian before use in breeding, pregnant, or lactating dogs. In all cases, the potential benefit of flea prevention (preventing flea anemia in newborn puppies, reducing flea allergy dermatitis in the mother) must be weighed against the potential risk of the specific product for the individual dog. Your veterinarian should make this recommendation based on your dog’s specific circumstances.
Generally, no — and specifically, combining products from the same drug class can increase the risk of adverse effects without adding meaningful benefit. Using both a Seresto collar (imidacloprid + flumethrin) and a Frontline Plus topical (fipronil) simultaneously is generally considered lower-risk because they use different drug classes, but even this combination should be discussed with your veterinarian. Never combine two isoxazoline products (e.g., NexGard and Credelio, or any oral isoxazoline with Bravecto Quantum). Never use K9 Advantix II alongside any other product containing permethrin. For dogs with very heavy tick exposure in endemic regions, some veterinarians do recommend a collar alongside an oral product using different mechanisms — but this should always be an explicit veterinary recommendation for your specific dog, not a decision made independently.
If your dog ate a flea chew significantly before the scheduled dose date, contact your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 (fee may apply) immediately. Do not wait for symptoms to appear. Early information to have ready: the product name, active ingredient(s), the dose your dog received, your dog’s weight, and the date of the previous dose. For most healthy dogs who accidentally receive one extra dose from the same product, the risk is considered low, but individual factors matter significantly. For isoxazoline class products in a dog with a history of seizures, any extra exposure should be treated as urgent. The ASPCA Poison Control line is staffed 24/7 by veterinary toxicologists and is the most reliable resource for real-time guidance.
Honestly, no — not for meaningful long-term protection. Essential oils (tea tree, lavender, eucalyptus, peppermint) applied to dogs can cause toxicity ranging from skin irritation to serious neurological effects, particularly in smaller dogs. Diatomaceous earth can cause respiratory irritation and does not provide reliable systemic protection. Apple cider vinegar sprays have no meaningful clinical evidence of efficacy against flea infestations. The ASPCA Animal Poison Control Center specifically warns against several essential oils commonly marketed as “natural flea repellents.” For a dog that genuinely cannot tolerate any FDA-approved product (a rare scenario), the most practical approach is rigorous environmental management — frequent vacuuming, hot-water washing of bedding, yard treatment, and physical flea combing — combined with veterinary supervision. For dogs with chemical sensitivities, Frontline Plus and the Seresto collar generally represent the lowest-risk conventional options with the most established safety records.
Sources: Flea life cycle 95% off-host: AVMA / veterinary parasitology textbooks; ASPCA Animal Poison Control 888-426-4435; FDA.gov CVM isoxazoline alert (breeding females Bravecto; consultation recommended); FDA.gov Bravecto Quantum approval (safety established when dosed 5x recommended every 4 months; elevated liver enzymes in adverse events; breeding female guidance); Merck Animal Health March 2026 (field study 0.9% seizure rate; consistent with general population); ASPCA Poison Control essential oils toxicity warnings; Frontline Plus label (safe for breeding, pregnant, lactating); Seresto label (safe for breeding, pregnant, lactating); NexGard/Simparica labels (consult vet for breeding dogs); K9 Advantix II (permethrin combination contraindications)
Allow location access when prompted to find the most relevant resources near you. Prescription flea products including Bravecto Quantum require a licensed veterinarian. Always report adverse reactions to both your vet and the FDA.
- Step 1: Choose duration based on your life, not just your dog’s. If you have a consistent routine and remember monthly applications, a monthly product works well. If you travel frequently, have a complex medication schedule, or simply find it difficult to remember monthly doses, a longer-duration product (Bravecto Quantum at 12 months, Seresto collar at 8 months, or Bravecto chew at 12 weeks) dramatically reduces the chance of unprotected periods. A missed monthly dose is the leading cause of flea infestations in treated pets.
- Step 2: Discuss your dog’s full health history before choosing any product. Dogs with a seizure history, neurological disorders, or those on anti-epileptic medications should avoid isoxazoline products (Bravecto, NexGard, Simparica, Credelio, Revolution Plus) unless a veterinarian explicitly approves it. For these dogs, Frontline Plus or the Seresto collar are the strongest long-term alternatives without the isoxazoline class warning.
- Step 3: Treat the environment simultaneously, not just the dog. Vacuum all carpets, wash pet bedding in hot water, and apply an IGR-containing premise spray when starting or restarting flea prevention after any gap. The home environment holds 95% of the flea population as eggs and larvae. No dog-applied product alone can resolve a household infestation without environmental co-treatment.
- Step 4: Keep all pets in the household on protection. A single unprotected cat or dog in the home acts as a flea reservoir, continuously reinfecting treated animals. If budget is a constraint, discuss with your veterinarian which animals pose the highest risk and prioritize accordingly — but ideally all pets should be protected simultaneously.
- Step 5: Report any adverse reactions promptly and accurately. If your dog develops vomiting, lethargy, tremors, or seizures after starting a new flea product, contact your veterinarian immediately. Keep the product packaging and note the exact date of administration and the dose. Report adverse events to the product manufacturer and to the FDA at fda.gov/animal-veterinary/report-problem/report-suspected-adverse-drug-events. Your report contributes to post-marketing safety surveillance that protects future dogs.
- Never use permethrin-containing products (K9 Advantix II) in households with cats. Permethrin is highly toxic to cats. Even a treated dog brushing against a cat before the product has dried can cause life-threatening permethrin poisoning. This includes contact through shared bedding, furniture, or grooming.
- Never use dog flea products on cats. Spot-on products formulated for dogs — including those containing permethrin, high-dose imidacloprid, or any isoxazoline — can be severely toxic or fatal to cats even in small amounts. Always purchase species-specific products.
- For adverse events: ASPCA Animal Poison Control Center: (888) 426-4435 (available 24/7; a fee may apply). Have the product name, active ingredient, your pet’s weight, and the dose administered ready before calling. Time is a factor in toxin management.
© BestiePaws.com — This guide is independently researched and does not constitute veterinary medical advice. We are not affiliated with, compensated by, or endorsed by any manufacturer of the products described. All drug facts, approval dates, and safety information are sourced from official FDA publications and peer-reviewed research as of March 2026. Drug labels, indications, and safety profiles change — always consult the current product label and your veterinarian before use. ASPCA Animal Poison Control: (888) 426-4435 • FDA Adverse Event Reporting: fda.gov/animal-veterinary/report-problem • Always verify current product labels with your veterinarian.
Primary sources: FDA.gov/animal-veterinary CVM (isoxazoline safety alert last updated Aug 2019; Bravecto/NexGard/Simparica/Credelio/Revolution Plus; muscle tremors, ataxia, seizures; safe and effective for majority of animals; manufacturers: Merck 800-224-5318, Elanco 888-545-5973, Boehringer Ingelheim 888-637-4251, Zoetis 888-963-8471); FDA.gov CVM CVM Update (Bravecto Quantum first approval July 10, 2025; first FDA-approved drug 8–12 months flea/tick dogs; dogs 6 months+ 4.4 lbs+; vet-administered subcutaneous injection); Merck Animal Health press release July 10, 2025 (Bravecto Quantum: 12-month fleas + black-legged, American dog, brown dog ticks; 8-month lone star tick; ≥99% effectiveness; 450M+ Bravecto doses worldwide; Edison Awards 2024; S&P Global Awards 2024 Best New Companion Animal Product); Merck Animal Health / MSD Animal Health press release March 18, 2026 (expanded Bravecto Quantum label: +Asian longhorned tick H. longicornis + Gulf Coast tick A. maculatum for 12 months; 0.9% seizure rate 2/225 dogs consistent with general dog population; safety demonstrated 5x dose every 4 months for 6 doses; available veterinary clinics since Aug 2025); FDA.gov Bravecto Quantum FOI Summary (clinical field study S19038-00; geometric mean effectiveness >99%; flea counts significantly reduced p<0.0001 all post-treatment visits); NCBI PMC “Survey of canine use and safety of isoxazoline parasiticides” (32,374 FDA reportable AEs 2013–2017; NexGard 6.9% seizure; Bravecto 2.8% seizure; Simparica 20.5% seizure in AE reports; EMA comparison); us.bravecto.com (≥99.8% flea kill; 2-hour onset; 3–6x more flea-free vs Frontline Plus 12-week study; FAD 86–100% resolution; topical >99% at 24h, 100% at 48h; lone star tick 8 weeks only); Allivet.com (Seresto 8-month imidacloprid + flumethrin; kills within 24h first application; kills within 2h after; 7 weeks+; safety-release buckle; waterproof; safe breeding/pregnant/lactating); BudgetPetWorld.com (NexGard afoxolaner 4-hour onset; Simparica Trio: sarolaner + moxidectin + pyrantel; 8 weeks+ 2.8 lbs; tapeworm prevention indication per FDA labeling change); Frontline Plus official label (fipronil + s-methoprene; monthly 30 days; 8 weeks+; waterproof; 12 hours adult kill; no isoxazoline class; safe breeding/pregnant/lactating); K9 Advantix II label (imidacloprid + permethrin + pyriproxyfen; 7 weeks+; permethrin fatal to cats; repels mosquitoes/biting flies/gnats; monthly); ASPCA Poison Control 888-426-4435 (essential oils toxicity; permethrin cat toxicity)