Will these products actually work if my pet gets wet in the rain, or if I shampoo him?

If your pet gets wet in the rain during a short walk, this will not interfere with the effectiveness on any flea control product. The Allergroom Shampoo is proven not to reduce the effectiveness of other flea control products such as Frontline and Advantage. The effectiveness of some sprays may be reduced if the pet is washed with a harsh shampoo or detergent soap.