You can also use a regular pet shampoo with orange essential oil added to it (which can be found at most health food shops), or a shampoo that has naturally added limonene (citrus extract).
The active ingredient is d-limonene, & it works as a contact kill, but has no residual properties. It may also be a repellant. We had bedbugs from May to December last year, & Murphy’s Oil Soap, which contains d-limonene, killed most of the bedbugs we found in our furniture. It also killed earwigs & a couple of other bugs we had in the basement. Having bedbugs has taught me more than I ever wanted to know about insecticides!