The skin itches and pimples when scratched

The skin scratches itches this kind of phenomenon possibly is the allergy creates, most sees is the acute urticaria, or is the allergic dermatitis, this kind of situation often and has eaten some allergic food related, for example has eaten the seafood, the cow, the mutton and the spicy stimulation food, or silkworm chrysalis and durian and so on often causes the allergic food, may cause the skin to scratch itches and has the appearance of the pimple. It may also be associated with immune system diseases, such as thyroid disease, vasculitis and systemic lupus erythematosus.