Flea bites don’t always itch, and in fact, some people have little to no allergic reaction to flea bites.
For most people, flea bites cause severe itchiness and a raised red bump where they have suffered a flea bite.
Fleas inject certain enzymes into the skin in order to numb the area as to avoid detection, as well as to prevent blood coagulation.
The enzymes cause an allergic reaction in most people, similar to what happens when you’re bitten by a mosquito bite, and this causes the itchiness and swelling.
Different flea bites on a single individual can vary as to their degree of itchiness. Additionally, some people are not allergic to flea bites at all and suffer no itchiness or adverse reaction to them.