Virtually all Finns are sensitized to mosquito bites already during childhood. Skin reactions caused by mosquito bites vary from rapidly appearing urticarial wheals to persistent itching papules. Allergic shock is fortunately extremely rare. The symptoms are strongest in early summer. Immediate symptoms result from proteins that get into the skin along with mosquito saliva and induce the production of IgE class antibodies by the body. The originating mechanism of delayed symptoms is unclear. Both immediate and delayed symptoms of mosquito allergy can be relieved with antihistamine drugs.