Bob martin double action spot on large dogs 10 25kg is effective and gentle and can be used on puppies from 8 weeks of age the specially developed double action formula will kill fleas on contact before they can lay eggs which therefore break the flea life cycle kills flea larvae in the pets immediate surroundings eg bedding and resting areas which prevents re infestation with up to 12 weeks protection 3 treatments fleas on dogs are killed within one day following treatment one