Sign one:

The dog is constantly itching or shaking. This could be an infestation of lice, fleas, or mange mites.

Sign 2:

Scabs, pustules, and even hair loss appear on the dog. This is most likely infected with scabies mites.

Sign 3:

When brushing the dog, small black particles were found. After the particles were dissolved in water, they were blood-colored. This is hard evidence of fleas.

Sign 4:

The dog suddenly became thin, with obvious ribs. This may be an infection with internal parasites such as tapeworms, roundworms, hookworms, etc.

Sign 5:

The dog is coughing frequently, or is short of breath. This could be heartworm or toxoplasma infection.

Sign 6:

A worm was found in the dog's vomit. This is most likely a roundworm infection.

Sign 7:

The dog pulls out black stools, bloody stools, or white particles and worms in the stools. This could be an infection with hookworms, whipworms, coccidia, roundworms, tapeworms.

Sign 8:

Your dog's gums and eyelids are pale, which means your dog is anemic and probably infected with some kind of internal parasite.

Sign 9:

The dog is constantly rubbing its butt on the ground, which is very itchy. It's very likely that tapeworms are at work!

Actually, dogs with parasites may not have obvious symptoms, so for the health of dogs, regular deworming is very necessary!