The early phase reaction is the body's immediate response to what it perceives to be a hostile attack. As the immune system is reacting against a harmless allergen the histamine serves no useful purpose and instead causes an increase in the blood supply, leakage of fluid from the small blood vessels and local irritation. This may manifest itself in swelling, itching and redness (i.e. bee sting or nettle) or in the case of allergic rhinitis (hayfever) the production of excess watery secretions (i.e. runny nose, sneezing and itchy eyes).