Why do we (humans/mammels) itch?

Question

Do other species itch? i.e. amphibians, marsupials, birds?

Answer 1

Itching is the result of the body's reaction to histamines, the same chemicals that cause us the discomfort and suffering of allergies. Minor itches are incidental and are caused by minor fluctuations in chemicals on your body. But prolonged or severe itching is usually indicative of something being wrong with your body, such a skin condition, an insect bite, or an allergic reaction. In that sense, it's a defense mechanism against more severe effects of such conditions, because it alerts you to do something about it. Because you felt the itch, you might apply an anti-fungal cream, or remove a tic from your skin.

Many animals other than humans itch. In particular, dogs are often seen scratching their ears with their paws, while large wild animals will rub up against trees or rocks to alleviate itching. Animals cannot treat itches as effectively as people can, of course, but this mechanism can still remove a parasite or chemical from the surface of the skin.