The active ingredients in Seresto are locked within the collar and released at very low doses, making Seresto safe for use around families and children. This has been confirmed through multiple safety studies. However, as with any flea and tick treatment, there are some standard safety procedures you should follow. Please check the label insert before using it.

If your spaniel over 18 lbs (8 kgs) you need a large size.

You should get Seresto for Large Dogs since it is for dogs over 18 lbs. The collar is 27.5 inch and is highly adjustable.

Yes, Seresto collars are waterproof, bathing your dog won't reduce effectiveness.

The collar is 27.5 inches (70 cm). It shouldn't be any issues on effectiveness as long as it fits his neck.