Spot-on applied wrong on Labrador? Here's what to do

It sounds like the spot-on didn't fail — the application just landed in the wrong place, which is more common than you'd think, especially with Labs who have dense coats. Before we sort the dog, it's worth knowing that 95% of fleas aren't on your dog at all — they're in your carpets, bedding, and soft furnishings — so even a perfectly applied spot-on won't solve things on its own. To point you in the right direction: what's your Labrador's approximate weight, how bad does the infestation look right now, and have you done anything to treat the home yet?

That explains it — if the product sits on the coat rather than the skin, it can't absorb and spread the way it's supposed to. The good news is the flea dirt tells us what we're dealing with, and at 32kg your options are straightforward. Given he's been scratching for two weeks and the house is untreated, you're at the point where you need something reliable and fast-acting on the dog. Can I ask — is he on any regular medication, and does he have sensitive skin or any known reactions to treatments?

Perfect — that gives you a clean run at the best option. For a 32kg Lab with an active infestation, I'd go with Frontline Plus for Large Dogs. It contains two active ingredients: fipronil kills adult fleas fast, and S-methoprene stops the eggs and larvae from developing, which is exactly what you need when things have been building for a couple of weeks. The critical thing with application is to part the fur fully at the base of the neck — right at the skin — before squeezing. Don't rub it in; just let it spread naturally from that one point. The coat on a Lab is deceptive; you genuinely need to feel the skin before you apply. At the same time, you'll need to treat the house. A spray like Indorex Defence Household Flea Spray will handle the environment — one can covers an average home and kills larvae and eggs for up to 12 months. Without that step, the scratching will likely return within a few weeks regardless of what you put on him.

You should see adult fleas dying off within 24 to 48 hours of a correct application. The scratching, though, can persist for up to two weeks even after the fleas are gone — partly because flea saliva causes an allergic response in the skin that takes time to settle, and partly because any remaining eggs in the environment will keep hatching for a while. If he's still scratching heavily after two weeks with the house treated as well, it's worth a vet visit to rule out a flea allergy dermatitis, which some Labs do develop after prolonged exposure. But in most cases, dog plus home treated together, you'll see a clear improvement within a week.

Only if it's been at least four weeks since the original application — don't double-dose within that window even if you know the first one didn't work properly, as that risks overexposure. If it's been less than four weeks, hold off and rely on the household spray doing its job in the meantime. From this application forward, stick to the monthly schedule and you'll be in good shape. One tip: keep a note of the date you apply each time — it's easy to lose track, especially with a dog who looks fine once the fleas are gone.