I suddenly begin to itch all over my body and bumps appears and just as fast as it started it goes away including the bumps what is that?

I have this. They sound like Hives, the result of an allergic reaction or skin irritation. I find that it can be caused by changing wash powder to a different brand, by strong scented bath and body lotions and some fabrics. I also have it when I touch latex.

Taking an anti-histamine such as Piriteze (available from most chemist and supermarkets UK) should ease the symptoms. Try using products on your skin that are hypoallergenic, PH balanced and perfume free such as the 'Simple' skincare range. You could also try using wash powder that is designed for babies clothing as this is usually more mild. Keep a diary of what you eat or use around the time that you get a rash as this may help your GP to diagnose a cause.

It could have been a nervous response to a real or perceived threat.

If they come up after you shower or get in water...then it means you have dry skin...take some Vitamin E:)

An allergic reaction what you ate. Temporarilly overwhelm the immune system, bumps appear, then immune system caught up.