Mosquitoes and gnats bite with their mouth parts, they have a sucking snout. Only females bite and suck blood of which they need protein for their eggs. They inject saliva into the opening. Thus, the solidification of the blood is prevented. In itself, this is little dangerous unless they transmit disease-causing germs.
Fleas and lice bite too.
Bees, wasps, bumble bees and ants have an ovipositor which is transformed to a sting(er). Only the females are stabbing.
Most European ant species have lost their sting. Some species, including the red forest ant (Myrmica rubra) do still have the associated venom glands. The species Myrmicidae has a well- developed bite device.
Except for allergic reaction a bite or sting does little harm. You may have a day or three a bump that hurts and itches.
Itching is the tickling sensation that warns against insects and irritating substances. Itching is caused by the release of histamine into the skin, as allergic reaction (e.g. a mosquito bite) or when nerve cells are damaged. These reactionsoccurtwo to eighthoursafter the sting. (The stitch itself (of a mosquito, flee) you don’t feel.
Itching can be caused by the growth of new nerve endings, but a lot about the essence of itch we just do not know yet. The reaction of rubbing and scratching (also at healing sores) is difficult to explain. Rub over and around an injury can promote blood circulation and healing.
Scratching damages the skin and worsens itching.
The nerves that itch signals transmit are also sensitive to heat. This may explain why itching during cooling of the skin decreases. Cooling and distractions help.