How many days apart should internal and external deworming be?

Internal and external deworming for pets can be done simultaneously without needing a gap, because most external dewormers are topical drops or sprays while internal ones are oral, and their different mechanisms allow combined use. However, if both the internal and external dewormers are oral, it is best to leave 5-7 days between them to avoid irritating the dog’s stomach.

Because some dewormers are quite irritating, if vomiting, diarrhea or lethargy appears after use, take the pet to the vet promptly.