Fleas

@TheNxtStep05, yes, the "cone of shame" is one treatment that will take care of the problem 🙂, but you still have to have your Sims take their pets to the vet clinic for this, as was stated above.  The cone will be the cheaper treatment, but you can also get them the more expensive treatment and this will also work.  Then there is also the Wellness Treats that @Juliaj  mentioned.❤️  But this is an older thread (from almost 2 years ago) , so it isn't likely that @artkid19 still has this problem. 😉