After being bitten by a small insect, causing localized redness, swelling and itching how to do. First of all, after the bite of a small insect stimulates the local tissues of the skin, causing vasodilatation of the papillary layer of the dermis, plasma oozing, causing redness and swelling, which is a kind of allergic reaction. To use local anti-allergic reaction drugs, such as halometasone, budesonide, etc., with anti-inflammatory, anti-itching effect, but also anti-allergic effect, topical drugs can be localized dissipation. If the rash area is large, the whole body or limbs, trunk, are covered with scattered insect bite dermatitis, you need to take oral antihistamines to make it dissipate faster, such as loratadine, cetirizine, cyproheptadine, etc., and infusion of anti-allergy treatment if necessary.