Some are, but some can be very toxic. To be completely safe, you can get your products from your veterinarian. Check with your vet if you would rather get your flea and tick preventatives online or in a pet store. They will make safe recommendations. Some are, but some can be very toxic. To be completely safe, you can get your products from your veterinarian. Check with your vet if you would rather get your flea and tick preventatives online or in a pet store. They will make safe recommendations.