A urine stain that's dried and faded from view hasn't gone anywhere — it's just invisible in ordinary light, and a dog or cat will happily use the same spot again even after it's stopped looking like a stain.

This is a handheld UV device with 21 LEDs that make old, dried urine marks glow so they can be seen and treated, rather than guessed at. It runs on 3 AAA batteries, which aren't included, and Simple Solution's own note is to replace them once the light starts to dim.

• 21 UV LEDs
• Reveals urine marks invisible in normal light
• Runs on 3 x AAA batteries (not included)
• Handheld
• Pairs with a cleaning product such as a urine and odour remover

What it does and doesn't do. This finds stains, it doesn't remove them — it's a torch, not a cleaner, so you'll still need something like a urine and odour remover to actually treat what it reveals. The card doesn't say how long the batteries last, so it's worth keeping a spare set on hand rather than finding out mid-search.

Who it's for: owners trying to track down where a recurring smell is actually coming from, especially before a deep clean, or when a cat or dog keeps marking a spot nobody can see a mark on.