An insect bite usually causes a small red lump on the skin, but the size will vary depending on the insect that has bitten you. The bites can be very itchy, and sometimes painful, and usually disappear on their own after a few days.Mosquitos are probably the most common type of insect bite (particularly in summer) and in most parts of the world they are completely harmless. You should be careful in tropical and subtropical areas of the world though, as mosquitoes carry malaria parasites.Bed bugs, fleas, mites, gnats and midges all leave very small red marks that are usually painless (yet itchy) and often formed in small clusters. Horsefly bites tend to be bigger and much more painful, but again don’t often cause further problems. The bites you need to be careful with are tick bites because they can carry Lyme disease. If you notice a tick attached to your skin then you should have it removed and make sure to do this carefully and properly.