Itching, redness of the skin, discomfort, presence of fleas in the fur, flea «dirt» scattered on the skin (trupanion.com)
You may not even know that this is happening unless your pet starts to clue you in on the annoying presence of fleas. (patrickmahaney.com)
And certain pets can develop a severe skin condition from the simple presence of fleas or through a disease called flea allergy dermatitis in which your pet is allergic to the saliva of the flea. (fourpawsdublin.com)